Cauliflower, Broccoli gratin

Ingredients:
1 medium-large cauliflower about 2.1/2 kg. and small broccoli =(1-1/2 kg.cauliflower and broccoli florets)
1 package (320gr.) shredded mix cheese.(Saputo ItalianMozzarella,provolone,Gouda,Parmesan)

Baking dish 28x35cm. (11×15)
Water to boil the cauliflower and broccoli florets with 1 tablespoon salt

Ingredients for white sauce:
4 cups whole milk 3.25% tor coconut milk (his time I used organic coconut milk)
125ml.unsalted butter
6 tablespoons (100ml.) all-purpose flour
1/2 cup grated Parmesan cheese
1 teaspoon freshly ground black pepper
1 teaspoon freshly grated nutmeg
1/2 teaspoon coarse sea salt

Preparation:
1.Cut off the outer leaves of the cauliflower,then cut into equal-size florets,wash under running water drain.Wash and cut the broccoli into florets.
2.Heat water with 1 tablespoon salt,bring to boil add cauliflower and broccoli florets, boil for 2 minutes, remove keep aside in a drainer.
3.Start preparing white sauce,heat the butter in medium pan,add flour, mix with whisker for 1 minutes,gradually add the milk, or like this time (coconut milk) salt,nutmeg black pepper and cook by constantly stirring,until the sauce thickens,about 12 minutes.Take off from heat add the 1/2 cup Parmesan cheese mix,keep aside.
4.Arrange cauliflower and broccoli florets in greased baking dish, pour the white sauce evenly over them ,sprinkle with mixed shredded cheese.
5.Bake in preheated oven 425 degrees in the second level from the bottom of the oven, 25 minutes,or until the top is slightly browned.
Serve hot.