Cut the fillet into strips and fry lightly, keep the stock. Cut mushrooms into slices and onions into cubes and sauté as well. Keep the brew from it.
Cook the spaetzle and then drain well. Butter a baking dish. The ingredients are layered as follows:
Spaetzle, meat, champions, onions, salt and pepper; Sprinkle with cheese at the end. Mix the stock, processed cheese, creme fraiche and cream and pour over the casserole. Bake at 200 degrees for about 30-45 minutes.