For the pasta-ham casserole, dice onions and ham and sauté in butter. Then add 1 tablespoon of flour and stir until browned. Deglaze with milk (and whipped cream to taste).
Add the egg yolks while stirring and bring to the boil. Season to taste with parsley, pepper, nutmeg and Parmesan cheese. Pour into the baking dish with the cooked pasta and sprinkle with cheese.
Bake at 200 °C for about 30 minutes.