Clean the spinach well, remove the large stalks and pull apart a little.
Peel and chop the onion and garlic. Fry the onion and garlic in olive oil, then add the spinach and sweat until it has collapsed. Finally, season with pepper, salt and nutmeg.
For the potato gratin, peel the potatoes and grate them into fine slices.
Grease the baking dish with a little butter and rub a clove of garlic in it. Put the potatoes and half of the cheese in the baking dish and mix everything together.
Then mix the milk with the 250 ml cream and season the mixture with salt, pepper, nutmeg and the other clove of garlic. Spread everything over the potatoes and put in the oven at 200 ° C for 55 minutes.
Then pour the eggs with the 6 tablespoons of cream over the pre-baked potatoes and sprinkle with the remaining cheese and the flakes of butter and bake the whole thing again for 30 minutes at 200 ° C.