Peel and wash the potatoes and cook them in boiling salted water for about 20 minutes. Drain and press through a potato press while still lukewarm. Add 1 egg yolk, flour and starch, season with salt and nutmeg and knead well with your hands. For the filling, peel and finely chop the shallots. Clean and wash the leek and mushrooms. Finely dice 1 stick of leek and half of the mushrooms. Heat the oil in a pan.
Sauté the shallots in it. Add the leek and mushroom cubes and steam for 3-5 minutes. Season with salt and pepper. Remove from the pan and set aside. In the meantime cut the remaining leek and mushrooms into fine slices and cook in the frying fat for about 5 minutes. Season with salt and pepper. Deglaze with broth and bring to the boil. Add crème fraîche and stir in. Add sauce thickener while stirring, bring to the boil again and season to taste. Add 5-6 tablespoons of the sauce to the ravioli filling. Grate cheese finely. Wash the chives, dab dry and cut into fine rolls. Add the cheese and chives to the ravioli filling, except for a little bit for sprinkling, and mix. Roll out the dough on a floured work surface 4-5 mm thin.
Add sauce thickener while stirring, bring to the boil again and season to taste. Add 5-6 tablespoons of the sauce to the ravioli filling. Grate cheese finely. Wash the chives, dab dry and cut into fine rolls. Add the cheese and chives to the ravioli filling, except for a little bit for sprinkling, and mix. Roll out the dough on a floured work surface 4-5 mm thin. Mark approx. 12 rectangles (approx. 8x5 cm) on one half of the dough and add 1 teaspoonful of filling each. Spread the rest of the egg yolk all around and fold the other half of the dough over it. Press the edges well and cut out ravioli with a pastry wheel. Cook for 8-10 minutes in slightly boiling water at low heat. Remove and drain. Heat the butter in a pan and fry the ravioli in it on both sides for about 1 minute. Arrange the sauce on plates and sprinkle with chives. Serve with diced tomatoes and garnished with chervil
Spread the rest of the egg yolk all around and fold the other half of the dough over it. Press the edges well and cut out ravioli with a pastry wheel. Cook for 8-10 minutes in slightly boiling water at low heat. Remove and drain. Heat the butter in a pan and fry the ravioli in it on both sides for about 1 minute. Arrange the sauce on plates and sprinkle with chives. Serve with diced tomatoes and garnished with chervil