For the pasta casserole, boil the whole-grain croissants in salted water for about 10-15 minutes until bubbly, then drain. Heat vegetable margarine, chop onion and mushrooms and sauté in the margarine.
Mix everything together, season and put in a greased baking dish. Beat eggs with sour cream, milk and spices and pour over the pasta-mushroom mixture.
Bake in the oven at 200 °C for about 25-30 minutes.