First, wash the broccoli and separate the florets from the stem. Bring a large pot of water to a boil and blanch the broccoli in it for about 4 minutes. Then drain and place in a bowl of cold ice water.
Béchamel
In the meantime, prepare the bechamel. To do this, heat the milk in a pot. In a pan, melt the butter over low heat. Once melted, remove from heat and add the flour. Stir vigorously with a whisk to get a lump-free mixture. Return the pan to the heat and brown everything lightly.
Once the milk is hot, season with a little grated nutmeg and a pinch of salt. Then add to the butter-flour mixture and stir vigorously with a whisk to thicken over low heat. The mixture must be homogeneous and free of lumps. Cook the bechamel sauce over low heat for about 5-6 minutes until creamy.
Casserole
Now get a casserole dish ready and spread some of the bechamel sauce evenly all over the bottom of the dish. Drain the broccoli well and place it in the dish. Then cover with the remaining bechamel and season with pepper to taste.
Last but not least, finish with the grated parmesan cheese. Now bake the casserole in a preheated oven at 400°F/200°C top/bottom heat for about 20 minutes. The broccoli casserole is ready when a light golden crust has formed on the surface. Finally, remove from the oven and allow to cool briefly.Buon appetito!