Melt butter in a pot. Dust with flour and sweat it. Add milk, bring to the boil and simmer for about 2 minutes, stirring, season with salt, pepper and nutmeg. Remove sauce from heat and let it cool down, then stir in egg. Cut the crust off the bread
Line the bottom of a greased box form (25 cm long; 1.5 litre capacity) with 3 slices of bread. Cut the bread that sticks out smaller. Drizzle with some sauce
First spread 2 slices of ham on top, then 3 slices of cheese. Repeat with the remaining slices of bread, sauce, ham and cheese, then finish with a layer of bread, cover with the remaining cheese and drizzle with sauce. Press everything a little
Bake in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: see manufacturer) for 25-30 minutes. Remove the mould, let it cool lukewarm, turn out of the mould, arrange and garnish with parsley as desired. Serve with a leaf salad with a vinaigrette of olive oil and balsamic vinegar