1. Cut the squash into 1 to 2 cm cubes.

2. Peel and cut the potatoes into 1 to 2 cm cubes. Peel and roughly chop the onions. Remove the dark green part of the leek. Cut the white part into quarters lengthwise and then into small pieces.

3. Melt the butter in a pressure cooker or casserole dish. Brown the onions and leeks for 5 minutes, without letting them brown. Then add the squash and potatoes.

4. Heat the milk and pour it into the pressure cooker. Add 50 cl of very hot water and 2 stock cubes. Do not add salt. Close the pressure cooker and cook for 30 minutes (1 hour in a pressure cooker without pressure).

5. Meanwhile, rehydrate the porcini mushrooms in a bowl of lukewarm water for 30 minutes.

6. Finely mix the casserole preparation to obtain a velvety consistency. Add salt and pepper.

7. Serve in a bowl. Add a few drops of White Truffle Oil, Truffle Powder and the Porcini Mushrooms on top. For a crunchy touch, brown the Porcini Mushrooms in a pan over high heat before serving.

8. Serve very hot with a pot of thick crème fraîche, so that everyone can help themselves as they wish.