Finely chop the onion and sauté in butter fat in a pan. Wash the spinach leaves, remove the stems and add them to the pan. Peel two small cloves of garlic and add one piece to the pan with the spinach leaves with onions.
Melt the butter in a small saucepan, add two tablespoons of flour, stir and mix a bechamel sauce with whole milk. Beat the bechamel sauce with a hand blender until frothy. Dice the mountain cheese and add to the sauce. Now stir the sauce every now and then until the cheese has melted. Season to taste with salt, pepper and herbs.
Finally, add the spinach leaves with onions and garlic from the pan to the saucepan and stir.
This delicious leaf spinach cheese foam sauce tastes great with spaghetti that has been drizzled with a little olive oil after boiling in salted water and draining.