Melt the butter in a pan, then add the flour and stir.

Pour half a glass of milk and stir. Keep adding the milk and keep mixing, don’t let it stick to the bottom. Add the nutmeg, then salt and pepper to taste.

When the sauce gets creamy, set it aside. If it gets too thick when adding it later to the lasagna, add more milk.

Follow the instructions on the package to cook the lasagna sheets.

Dice the onion and stir-fry it in a pan with olive oil and a pinch of salt until browned. Add the spinach and the garlic, and keep stirring for 5 minutes.

Preheat the oven at 200ºC.

In a deep baking tray, place a layer of lasagna sheets at the bottom, then a layer of tomato sauce, then a layer of the onion-spinach mix, and repeat all the layers.

Pour the bechamel on top of the lasagna and cover it completely, then sprinkle the cheese, oregano, and parsley on top.

Bake for 15 minutes at 180ºC.