Mix the flour and egg together, knead well until you have a smooth, even dough. Cover and let rest for 30 minutes under a clean kitchen towel.

Quickly blend the stracciatella cheese and place it in a fine mesh strainer to drain any excess liquid. Finely chop the prosciutto with a knife and mix it with the stracciatella.

Roll out the dough with a rolling pin or, even better, a pasta machine, to make two thin sheets. Place small amounts of filling at regular intervals on the first sheet, cover with the second sheet, and use a fluted pastry wheel to cut out the ravioli.

Boil the ravioli in salted water for 5 minutes, then sauté them in butter with chopped sage leaves. Serve and season with black pepper and a sprinkle of grated Parmesan cheese.