Clean and wash the cauliflower and cut into florets. Cook in 1 liter of lightly salted water for 10-15 minutes until al dente. Peel onions and cut them into fine pieces. Cook the potatoes in 10-15 minutes until they are completely soft, peel and cut into slices.
Heat the oil, fry the onion in it, add the minced meat and fry until crumbly, season with salt, pepper and thyme.
Put the ingredients in layers in a baking dish, start with the potato slices, then add the minced meat and the cauliflower, the last thing is another layer of potatoes.
Pour the hollandaise sauce evenly over it and sprinkle the cheese on top. Bake at 200 ° (convection: 180 °) for about 20 minutes.