Preheat the oven to 180 ° C fan oven. Place the potatoes in cold salted water, bring to the boil and cook for 8 minutes over medium heat. Drain, rinse with cold water and drain. Coarsely mash with a fork.
Heat the butter in a sufficiently large saucepan, add the onions and fry over a low heat for about 5 minutes. Add the white cabbage and stir-fry for 5 minutes. Add the potatoes and season with salt and pepper to taste. Remove from the heat and stir in 2 tablespoons of cheese. Put the mixture in a baking dish and sprinkle with the rest of the cheese.
Bake on the middle rack for 20 minutes.
If you don`t like the cheese layer so thick, you simply use less for sprinkling.