Fry the onion in the oil, if you want, add the minced meat and fry with it.
Add the leek, chopped white cabbage and the mushrooms, salt and pepper, cook for 6 minutes, add the soy sauce, season everything well. Mix in an egg yolk.
Peel the jacket potatoes and cut into slices, place in a flat baking dish, pour the (minced) vegetable mixture over it, sprinkle with the cheese. Baked in the oven until the cheese has melted.