Fry the onions in rapeseed oil and add the minced meat. After the minced meat is well done, stir in the tomato paste, green beans and mushrooms and season everything with a little salt and plenty of pepper.
First put the sliced potatoes in a buttered casserole dish and season them with a little salt and pepper, followed by the minced meat mixture. Finally, the sour cream and then the grated cheese are spread on top.
Bake the casserole at 200 ° C (175 ° C convection) for about 35 minutes. The cheese should be nice and brown and the potatoes should be done.