In a food processor, finely chop the mushrooms. Heat the oil in a frying pan and sauté the mushrooms for approx. 15 mins. until the resulting liquid has almost completely evaporated, allow to cool a little. Mix the mushrooms with the ricotta, parmesan, egg yolk and sage, season.
Unroll the pasta dough, cut in half lengthwise. Spoon 1 tbsp of the filling on the bottom halves of the strips of dough, evenly spaced. Brush the upper halves of the pasta strips with a little egg white, fold over the filling, press the edges down firmly, pressing out any trapped air. Separate the ravioli with a pastry wheel. Press the edges with a fork.
Cook the ravioli
Cook the ravioli in batches in simmering salted water for approx. 5 mins., remove with a slotted spoon, drain.
Heat the clarified butter in a pan. Sauté the mushrooms for approx. 5 mins. Add the butter and heat until it foams and smells slightly nutty. Add the nuts and sage leaves and fry for approx. 3 mins. Add the ravioli, mix carefully.