Recipe: Thomas Keller's leeks vinaigrette, pain de campagne and black winter truffle ravigote

Makes 6 servings

Hen egg terrine

• 250g egg whites
• 6g kosher salt
• 175g egg yolks

Leeks

• 150g Holland leeks (white portions only)
• 200g prepared veg blanc (see below)

Black winter truffle ravigote

• 375g water
• 40g Champagne vinegar
• 43g sugar
• 10g kosher salt
• 4g Pre-­Hy (see below)
• 18g extra-­virgin olive oil
• 30g minced black winter truffle

Pain de campagne croutons

• 100g extra virgin olive oil
• 30g 6mm crustless pain de campagne (crusts removed before cutting)
• 1 thyme sprig
• 1 garlic clove
• 3g kosher salt, plus more to taste

To complete

• 2 French leeks, green portions only
• Extra-­virgin olive oil
• Fleur de sel
• 18 thin slices black winter truffle, at least 16mm in diameter each (optional)

Special equipment

• Combi oven
• Chamber vacuum sealer
• 13mm round cutter
• 13mm flower-­shaped cutter

For the hen egg terrine

Preheat a combi oven to 85°C. In a blender, blend the egg whites and 2.5g of the salt on high speed for 8-10 seconds, until the whites are broken up. Strain the egg whites through a chinois into a container. Place the container, uncovered, in a chamber vacuum sealer. Run a complete cycle on full pressure to remove any air bubbles incorporated during blending. Stay at the machine, and if the egg whites begin to bubble over, stop the machine.

Blend the egg yolks and the remaining 3.5g salt on high speed for about 10 seconds, until smooth. Strain through a chinois into a deli container.

Place an eighth sheet pan into a 30cm x 40cm sous vide bag, leaving a 2.5cm border between the pan and the bag. Place in the sealer chamber and vacuum seal to line the pan. Place the lined pan in a container with a lid.

Gently pour 85g of the egg whites into a small deli container or other plastic container.

Slowly pour the egg whites onto the lined pan, holding the container close to the pan to avoid creating any bubbles. Use a small silicone spatula to move the whites into any areas or corners that are not filled. Cover the pan container with its lid and steam in the combi oven for about 10 minutes. Remove the container from the oven and uncover; the whites as well as all subsequent layers should feel firm to the touch after steaming.

Pour in 150g of the egg yolks, tilting the pan in each direction to form an even layer. Cover the container, return it to the combi oven, and steam for about 10 minutes. Remove the container from the oven, add another 85g of the egg whites (again being careful not to create bubbles when you pour them), cover, and steam for about 10 minutes. Uncover the container and cool the egg terrine in the refrigerator. It must be completely cold before portioning.

The hen egg terrine can be wrapped in plastic wrap and refrigerated for up to three days.

For the leeks

Preheat the combi oven to 88°C.

Remove the outer layer of the leeks, cut them in half lengthwise, and rinse to remove any dirt. Place the leeks in a sous vide bag with the veg blanc. Place the bag in the sealer chamber and vacuum seal. Steam in the combi oven until tender when pinched with your fingers, about 20 minutes. Submerge the bag of leeks in an ice-­water bath to chill. Refrigerate in the bag for up to three days before cutting.

For the black winter truffle ravigote

In the blender, blend the water, vinegar, sugar and salt on low speed for 15 to 30 seconds, until the sugar and salt have dissolved. With the blender running on low speed, add the Pre-­Hy and blend to combine, gradually increasing the speed to high.

With the blender running on medium speed, very slowly drizzle in the olive oil, maintaining the emulsion throughout the process.

Refrigerate in an airtight container for up to three days. Stir in the black truffle just before serving the dish.

For the pain de campagne croutons

Heat a medium sauté pan over medium-­high heat. Add the olive oil, then the diced bread, thyme, and garlic and toast the croutons, stirring continuously, for about two minutes, or until golden brown. Drain the croutons on paper towels and immediately sprinkle with the salt.

Discard the thyme and garlic and let cool.

The croutons can be stored in an airtight container overnight.

To complete

Bring a large pot of salted water to a boil. Blanch the French leek greens for two minutes and chill in an ice-­water bath. Dry on paper towels and cut into 1.25cm pieces. Toss with olive oil and season with fleur de sel.

Drain the cold Holland leeks and dry on paper towels. Working toward the root end, slice them on a 45-­degree angle into diamond-­shaped pieces about 2cm wide.

Punch rounds from each slice of truffle (if using) with a 13mm round cutter.

All components of the finished dish should rest at room temperature for about 20 minutes before plating.

Spoon 30g of the black truffle ravigote into each serving bowl. Using a small offset spatula, arrange three pieces of Holland leek facing different directions in a triangular formation at the bottom of each bowl. Arrange three pieces of the French leeks around the bowl. Cut and remove a small corner of the terrine to enable you to lift out pieces of the terrine more easily. Punch the hen egg terrine with a 13mm flower-­shaped cutter and arrange the terrine cutouts in the spaces between the leeks. Just before serving, sprinkle the croutons on top and arrange a truffle round (if using) over each Holland leek.

For the veg blanc

Makes 600g powder base (enough for 10kg prepared veg blanc)

• 300g kosher salt
• 250g sugar
• 50g ascorbic acid
• Filtered water

Mix all the ingredients together and store in an airtight container at room temperature.

For every 100g prepared veg blanc needed, whisk together 100g filtered water and 6g of the powder base.

For the Pre-Hy (prehydrated xanthan gum)

We'd like to call special attention to one liaison that we find profoundly useful when it's properly diluted: xanthan gum. Xanthan gum is one of the most often used and versatile liaisons, but it is severely potent. Just a little bit can achieve dramatic results. Add too much, however, and it's time to "begin again". It's so powerful in powdered form that it's easily mismeasured. If you're off by a tenth of a gram, you can ruin a whole sauce. To solve this problem, David developed what we call prehydrated xanthan gum, or Pre-Hy, as it's known in both kitchens, in effect diluting the powdered xanthan gum and making it much easier to use, a real game changer for us.

• 1%: Emulsification
• 2% All-purpose Pre-Hy
• 3%: Bouillon consistency
• 5%: Velouté consistency
• 15%: Fruit or vegetable glaze (with 1% Ultra-Tex)

To make our all-purpose Pre-Hy, which is used throughout the book, put 1kg of water into a blender. With the blender running on low speed, shear in 20g of xanthan gum while slowly increasing the speed to high. The xanthan gum should completely hydrate in the water. If you have a chamber vacuum sealer, pass the mixture through a chinois into a container and place the container, uncovered, in the sealer chamber. Run a complete cycle on full pressure to remove any air bubbles incorporated during blending. It will produce a clear gel, which will contribute to the clarity of the sauce or purée it will eventually be used in.

Pre-Hy is cold-soluble, so it can be mixed directly into liquid in a Vita-Prep (or Vitamix) to add viscosity. At 1%, the Pre-Hy is the perfect aid in a powerfully bound mayonnaise and a useful stabiliser of simple emulsified oil-and-vinegar-based vinaigrettes. At 3%, it adds just a hint of body to an otherwise thin juice or broth. That's all it needs to hang on the palate a little longer and therefore add to the perception of depth of flavour and satiety.

When 3% is added to a beurre blanc or beurre monté, it becomes a stable butter glaze resembling a beurre fondue. At 5%, added to our classic creamy lobster broth or other creamy broths, it keeps the cream and stock perfectly emulsified and holds the frothy bubbles that we like so much. And finally, at the highest concentration, 15%, in tandem with a small amount of Ultra-Tex, marinades or poaching liquids can be thickened to coat fruits and vegetables in a shiny glaze.