Cut each slice of foie gras into 2 pieces and season with fleur de sel and pepper.
Beat the egg yolk with a little water to make an eggwash.
Lay the foie gras pieces onto 6 of the pasta sheets, leaving plenty of space between each piece. Brush the eggwash onto the pasta and then lay a second sheet on top. Press the pasta sheets together and then use a pastry cutter or ring to cut out each raviolo.
Brush the mushrooms clean. Peel and finely dice the shallots. Roughly chop the hazelnuts and the chervil.
Remove the stalks from 3 mushrooms and then cut the head of the mushroom into thin matchsticks. Set these aside for the moment. Dice the 3 stalks, along with the rest of the mushrooms.
Heat a saucepan and add a drizzle of olive oil. Add the shallots and a pinch of salt and cook for 3 minutes before adding the chopped mushrooms. Add enough chicken stock to cover the mushrooms and cook for 15 minutes. Season with salt and pepper and then add the cream and the hazelnut oil. Transfer to a food processor and blend until smooth.
Place the mushroom matchsticks in a bowl and gently combine with the chopped hazelnuts, chervil and hazelnut oil.
Bring the remaining chicken stock to the boil, reduce to a simmer and then add the ravioli and cook for 3 minutes.
Serve the cream of mushroom in soup bowls and add two foie gras ravioli to each bowl. Finish with a spoonful of the mushroom, hazelnut and chervil mixture and serve immediately.
«To prevent your ravioli from tearing or bursting when cooked, make sure there is no air trapped inside when you seal each raviolo. Use your fingertips to secure the pasta around the foie gras.»