For the cauliflower casserole, first peel the potatoes, wash them and cut them into fine slices.
Cut the cauliflower into small florets, wash, place in cold salted water for 10 minutes and then cook together with the potatoes in salted water for 15 - 20 minutes until al dente.
In the meantime, peel the onions and cut into fine cubes. Heat sunflower oil in a pan and roast the onion pieces and the bacon cubes in it. Spread the potato slices and the cauliflower florets evenly in a greased baking dish, then place the roasted onions and diced bacon on top.
For the sauce, stir the processed cheese with the cream and hollandaise sauce until smooth and season with salt, pepper, nutmeg, marjoram and lovage. Then pour the sauce over the casserole and spread the grated cheese as the top layer on the casserole.
Gratinate the cauliflower and potato casserole at 175 ° C (fan oven) for 20 to 25 minutes in the preheated oven.