Chefs fight invasive species with creative menus

This extreme sustainability is what Doug McMaster is exploring as part of a series of dinners this summer hosted at his zero waste restaurant Silo in Hackney Wick, celebrating invasive species, with the first shining a light on knotweed.

"There's a hysteria around Japanese knotweed," says McMaster. "We spray it with toxic chemicals to kill it, but with a fresh pair of eyes we can see potential in the waste and get creative, making things like sour beer, umeboshi pastes and cocktails."

McMaster partnered with chef Matt Orlando, previously of Copenhagen's Amass, to create dishes for the first knotweed dinner in June, with a menu beginning with a glass of sour knotweed beer and a starter of Japanese knotweed umeboshi.

Sour and rhubarb-like in taste and texture, the knotweed starter was balanced with Japanese fermented umeboshi pickle, while herbs and sour cream were used to cut through the sharpness. When introducing their first plate of food, McMaster and Orlando encouraged guests to eat with their hands to liken the experience to that of the chefs foraging for the plants on Hackney Marshes.

Foraging for invasive species is hard work, and McMaster says that the Silo team is stretched to be able to produce three dinners a year with the effort from the days spent foraging knotweed in the spring time – leave it too late into the summer season and the plant develops bamboo-like strength and becomes inedible.

McMaster's glut of knotweed was presented to guests at his dedicated dinner, but also brewed into 2,000 litres of a sour knotweed beer. The beer has been available during regular service at Silo, as well as downstairs in the Crate Brewery for punters to enjoy on Hackney Wick canal.

"That's nearly 4,000 pints," says McMaster. "We're not just going to talk about this – we're going to do something creative to put a dent in the problem."

McMaster admits that events like his limited dinners, while helping to get the message about invasive species out into the wider world, are still unusual. "The dinner was a one-off, but making 2,000 litres of knotweed beer turns invasive species into something positive and beautiful."

The menu [see panel] also showcases other invasive species, including Pacific oysters, grey squirrel and muntjac deer – all underused ingredients that can be delicious in the hands of an experienced chef. British venison, which while native is overpopulated in certain areas of the country and needs controlling, also features to help "balance the menu into something palatable, and to help ease people in".

Other sustainability supremos are also getting involved in the fight, with Hugh Fearnley-Whittingstall guest cooking in September with Himalayan balsam, which his beloved River Cottage is currently struggling to keep under control. Skye Gyngell recently created a menu focused on American signal crayfish.

McMaster describes these ingredients as "beyond abundant" to the point they are invasive: "It's a net positive," he says. "You're taking away something that needs to be mitigated. The only difference is that we'd want to forage knotweed until it's extinct and it's the same for the American signal crayfish."

American crayfish against the UK's white-clawed species

The UK's white-clawed crayfish have declined so significantly in numbers over the past 50 years that they are now a protected species due to the introduction of its American cousin, which have been decimating the native population. Due to its freshwater habitat, this species of shellfish has a subtle, delicate flavour, similar to its lobster cousins, but with a sweeter meat alike to langoustines. But chefs would be hard-pressed to get hold of crayfish from UK waters, with only a couple of traders of American signal crayfish operating up and down the country.

Bob Ring is one of those few UK traders. Better known as ‘Crayfish Bob', he calls himself an environmentalist and eco-businessman who is trying to navigate the many layers of politics that make it difficult for him to trade in crayfish. His main bugbear is the fact that since 2019 tighter restrictions have come into law, meaning it is now illegal to keep and sell live American signal crayfish in England and Wales, while transportation of the live species is under strict control and only applies to licence-holders.

"The trouble is, if you're a chef you want them supplied live, like lobsters, and to cook them yourself," says Ring. "But as the law stands at the moment, I can't trade in live crayfish."

A spokesperson from the Invasive Alien Species Team at Natural England tells The Caterer: "The changes are intended to help to protect our native species and freshwater environments and prevent the unintentional transfer of these species between water bodies."

Instead, Ring traps American signal crayfish from English waterways mainly in the south east and the Home Counties and – as a licensed supplier – transports them to a dedicated processing facility, where they are usually flash frozen to avoid quality degradation. He can also supply crayfish to customers ready-cooked in a Swedish style, where the crayfish are bought to the boil in a brine of salt, sugar, fresh dill, dill seed, fennel seed, bay leaves, black pepper and stout, before being transferred into a cold brine and left for 24 hours.

One such crayfish customer is Gosnells Meadery Taproom in Peckham, London, where Ring is hosting a series of Louisianna crayfish boils. Owner of Gosnells Tom Gosnell says: "Bob is doing an amazing job in ridding our waters of this pesky interloper. So guests can munch through all the crayfish they like, safe in the knowledge they are not only having a tasty supper, but also helping the environment."

Another way to overcome the pesky paperwork could be to can the crayfish at source, which McMaster points out is very on-trend, with tinned fish popping up on restaurant menus up and down the country.

"It's the most sustainable way of preserving food, down to the aluminium, which is endlessly recyclable. So if we were able to tin invasive crayfish in vast quantities we'd be doing something creative to put a dent in the problem. Like how we use waste at Silo – it's about turning a negative into a positive."

Will Murray, co-owner and chef at sustainable fine dining restaurant Fallow, has also dabbled in invasive species on his menus over the years. He uses Japanese knotweed as a play on rhubarb crumble and American signal crayfish in sauces and bisques, including Fallow's shellfish broth.

"It's a great product and these crayfish are everywhere, so we're trying to use as much of them as possible," he says. "When things are in season and growing wild in the UK we should use that resource – for example, knotweed could be compared to wild garlic. We could feed children Japanese knotweed and they wouldn't know it's not a regular crumble."

Murray admits he doesn't necessarily use invasive species because it's a moral responsibility, but because it tastes good: "It's a win, win, win – sustainable, delicious and at a good price point."

Grey squirrel is another invasive species that has been on and off the Fallow menu over the years, but Murray is currently struggling to get hold of the meat. "What we've had in recently isn't quite good enough," he says. "Our focus is sustainability, but it wouldn't go on the menu if it wasn't absolutely delicious."

Grey squirrel be gone

Another operator who made headlines for featuring grey squirrel on its menu is sustainable restaurant Native. Co-owner Imogen Davis recalls the moment chef and co-owner Ivan Tisdall-Downes created a grey squirrel lasagne in 2019, which led to its own ‘Not Native' dinner series focusing on various invasive species.

"Grey squirrel is a no-brainer for us, it's a delicious, lean meat – similar to rabbit or pheasant breast – and we slowly braised it into a ragu for the squirrel lasagne."

The recipe went viral, and subsequently divided opinion between guests, some travelling as far as Germany and the US to try Native's food, and others who didn't approve of eating "cute little squirrels".

Like Murray, Davis has struggled to get hold of grey squirrel recently, but she believes giving chefs access to a robust supply chain of invasive species would help normalise eating these unusual ingredients. "Sourcing things like crayfish and even squirrels isn't easy," she says. "And you're not allowed to cultivate knotweed so you need to be in the know to be able to forage it – and I've never been lucky enough to have it in my garden!" she jokes.

But Davis highlights there is a fine line between using ingredients that are plentiful, and potentially creating a market for produce that we are actively trying to eliminate.

"Similar to foraging – it's about taking everything in moderation. Grey squirrels are destroying habitats and local biodiversity, so they are being culled in some areas, same with muntjac deer, while Japanese knotweed is being poisoned with herbicide and ripped out of the ground. This turns these products into waste, which we should be using as a food source."

Davis says we "should be eating what we kill", pointing out that if a supply chain for human consumption is created then animals will be killed more humanely and plants won't be poisoned – which is a win for both the industry and environmental advocates.

But if the attempts at trading in crayfish are anything to go by, the legislative red tape may mean a robust supply chain may be some way off, so chefs should grab any opportunity to experiment. Davis advises: "Similar to seasonal produce, chefs must plan for invasive species to be here one week and maybe next week they can't get hold of it – because you can never guarantee it will be there."

Echoing both McMaster and Murray, Davis says: "With ingredients that are so bountiful, yet need controlling, it's an absolute no-brainer to put them on menus."

From Silo's invasive species menu

• Pacific oyster, mutton fat sabayon
• Crayfish tart, chive
• Japanese knotweed umeboshi, alliums, sour cream
• Lion's mane, crayfish head butter, tomato MSG
• Squirrel kofta, yogurt, celeriac
• Muntjac, shiitake miso treacle, alliums
• Venison garum parfait, chorus, vintage apple
• Knotweed ripple ice-cream, Mexican marigold

Muntjac scrumpet with aïoli from Fallow

For the aïoli

• 1 egg yolk
• 1tsp Dijon mustard
• 1tsp white wine vinegar
• A pinch of salt
• 2 cloves garlic, crushed
• 1 cup vegetable oil
• 1tsp lemon juice

In a cylindrical container place the egg yolk, mustard, vinegar, salt and garlic. Mix these ingredients until fully combined with either a stick blender or handheld whisk. Whilst blending/mixing slowly pour in the oil in a steady stream. The liquid should start to thicken slightly and go pale.

Once the oil is fully incorporated, add the lemon juice. Check the aïoli for seasoning and refrigerate.

For the muntjac scrumpet

• 2tbs vegetable oil
• 1 muntjac haunch
• 4 banana shallots, thinly sliced
• 2 cloves garlic, whole
• 5 juniper berries
• 3 whole cloves
• A sprig each of rosemary and thyme
• 1 cup red wine
• 2 cups beef stock
• Pinch salt and pepper
• 3tbs plain flour, seasoned with salt and pepper.
• 2 medium eggs, beaten
• 1 cup panko breadcrumbs
• Oil, for deep-frying

Preheat the oven to 150°C.

Place an ovenproof pan on high heat with the vegetable oil. Once hot, add the muntjac haunch and give it a heavy sear on all sides. Once it is browned add in the thinly sliced shallots and the garlic cloves. Sautée for two minutes until soft and fragrant.

Add in the spices, rosemary and thyme then deglaze with the wine and stock. Place a lid on the pan and place in the oven for 3-4 hours or until the venison falls off the bone.

Once cooked, place the haunch into the fridge and allow to cool completely in the cooking liquid. This will allow the meat to stay extremely juicy.

Remove from the liquid and portion the meat into 2cm x 8cm portions.

Next prepare the breading by placing the flour, egg, and bread into three separate bowls. Start by placing the portions into the flour, dusting off excess, then follow through to the egg and then the panko breadcrumbs.

Preheat a medium-sized pot and pour in roughly 8cm-9cm of vegetable oil. Bring the oil up to roughly 180°C.

Carefully place the breaded meat into the hot oil and fry for roughly two minutes or until golden brown. Remove from the oil and place on a piece of kitchen paper. Season with a little more salt and serve with the aïoli.

A spotlight on invasive species

Japanese knotweed

Japanese knotweed is native to Japan, Taiwan and Northern China, and was introduced to the UK in the 19th century as an ornamental plant.

It can cause havoc on buildings and railways as it has a detrimental impact on native biodiversity, due to its ability to form dense monocultures and to regrow from tiny fragments of the plant's stem.

Chefs must keep in mind that they mustn't throw away any trimmings from knotweed, because this may cause it to invade a new habitat. Trimmings must be burnt or boiled until completely dead before discarding.

Pacific oysters

While large Pacific oysters are legally cultivated in the UK, they are pushing the native British oysters out of their habitat. Their subsequent abundant numbers are causing a threat to protected estuaries, where traditionally muddy shores are becoming enveloped by oyster reefs which are impacting the feed grounds for birds and other native wildlife.

Grey squirrel

Native to North America, the grey squirrel was first introduced to the UK by the Victorians. They are larger than the native red squirrel and also reproduce more successfully.

They also carry a disease called squirrel pox, which the greys seem to be immune to, but kill the native reds. Grey squirrels impact woodlands by stripping bark off trees to feed on the softer inner layers, causing damage and in some cases killing the tree.

Grey squirrels can be bought through a semi-traditional supply chain through companies such as the Wild Meat Company, which can provide the ethical meat "oven ready", weighing in at around 225g.

Signal crayfish

The American signal crayfish were first introduced to UK waters in the 1970s when an opportunity to farm and sell crayfish to European neighbours came about as countries like Sweden and Scandinavia were struggling with their populations, which were suffering from disease.

The US variety seemed immune to this plague, but no one at the time realised they too were the carrier of disease, which has since decimated the UK's own white-clawed crayfish population – now a protected species.