For the ravioli:
Whisk flour with eggs and salt, knead until a smooth dough is formed and then rest at room temperature for about half an hour.
For the filling:
Cut the gorgonzola into cubes and heat with milk in a water bath until the cheese is soft. Stir the mixture with a fork until it forms a smooth cream. Chop the walnuts and mix them with a little Parmesan into the mixture, season with pepper and a pinch of nutmeg.
Roll out the dough thinly on a little flour or in a pasta machine and cut out round pieces of dough with a glass. Put some filling on the dough piece form and cover with the second dough piece.
Press the edges together and make the ravioli in salted water for 3 minutes.
Melt the butter, pluck the sage leaves and form them in the butter.
Arrange the ravioli on a plate, cover with a little bit of sage butter and sprinkle with Parmesan cheese.