In the meantime, peel the onion, dice it finely and sauté in the butter until translucent. Add the minced meat and fry until crumbly, season with herb salt, cayenne pepper and nutmeg.
Preheat the oven to 180 degrees.
Spread half of the spinach in a baking dish and place half of the minced meat on top. Then put the remaining spinach and finally the remaining minced meat in the pan. Mix the cream with the cheese and pour over the casserole.
Bake the casserole in a hot oven for about 20 minutes.