Boil the potatoes, drain them and then mash them. Process with milk and butter into a mashed potato. Season with fried onions, salt and pepper, possibly nutmeg. Put the mixture in the previously greased baking dish. Make 4 hollows in the mashed potatoes with a tablespoon. Beat the eggs and place one egg in each well. Sprinkle the casserole with cheese and bake in the oven at around 180 ° C for 20 minutes, until the cheese has a golden color.
Add vegetables and you have a complete main course.