Defrost the peas and carrots. Grate cheese finely. Heat 1 tablespoon of fat in a pan and fry the potato noodles until golden brown. Peel and finely dice the onion. Heat 1 tablespoon of fat in a saucepan and sauté the diced onion.
Dust with flour and sweat for about 2 minutes. Deglaze with broth while stirring and let simmer for about 5 minutes. Whisk egg and milk and add while stirring constantly. Add half of the cheese and season to taste with salt, pepper and nutmeg.
Put the potato noodles, peas, carrots and salami in a greased casserole dish. Pour sauce over it and sprinkle the remaining cheese over it. Gratinate in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for approx. 10 minutes.
Remove and serve immediately.