Make the ravioli dough by placing the flour in a mound on a work board. Make a well in the center and put in the eggs and mix together. Knead the dough until it becomes smooth and consistent. Let it rest for at least 30 minutes.
In the meantime, boil the chicken breast in water with a bouillon cube. When it is cooked, remove it from the broth and mince it. Finely chop the Raschera cheese and mix it with the minced chicken breast, the egg, grated nutmeg, salt and pepper.
Roll the dough into a very thin sheet. Cut out squares with a knife and fill each square with a small heap of mixture and fold it over. During this procedure cover the rest of the dough to prevent it from drying.
After making the ravioli, brown the leek cut into thin slices in a pan with butter. Remove from the heat and toss in the pan fresh cream, salt and pepper.
Bring the water to a boil. Salt it and drop in the ravioli. Cook them "al dente" (underdone) and drain them in a strainer. Place them in the pan with the leek sauce.
Put the pan over the heat for some minutes. Let the ravioli flavour and the sauce thicken. Serve hot and sprinkle with grated Parmigiano.