Peel and finely chop the onion. Place the ham slices on top of each other, first cut into strips, then into fine cubes. Heat butter in a pot. Sauté onion in it
Add the diced ham, fry briefly. Sprinkle with flour and sauté. Deglaze with 1/8 l water and milk. Stir in stock. Bring the sauce to the boil, simmer for about 5 minutes while stirring
Boil up about 1 l salted water. Coarsely chop the walnuts. Melt parmesan and ricotta in the sauce while stirring. Stir in the nuts and season to taste with salt and pepper
Add the ravioli to the boiling water and let it stand for 2 minutes. Wash and finely chop the basil. Noodles
lift out, arrange with sauce and basil