Prepare the purée. Heat the knob of butter in a saucepan with 50ml of water. Dice the butternut squash and cook it in the butter, covered, for about 10 minutes over medium heat, until very tender. Pour the cream into the purée and stir vigorously. Roughly chop the hazelnuts. Stir them into the purée.
- Prepare the ravioli. Dice the Saint Agur Blue Cheese. Lay the ravioli sheets on a clean, dry work surface. Using a round cutter, cut out circles from the ravioli. Place a teaspoon of butternut squash puree in the center of each circle. Add a piece of blue cheese. Brush the edges of the ravioli with egg yolk, then seal them by pressing firmly with the tines of a fork.
Prepare the sauce. Wash and slice the mushrooms. Sauté them in a knob of melted butter. Add the sage and cream. Heat gently.
Cook the ravioli. In a saucepan, bring the vegetable stock to a boil. Poach the ravioli in batches of 6 in the simmering stock. Arrange the ravioli on plates, top with the porcini cream sauce, and sprinkle with chopped hazelnuts.
