Ricetta patate gratinate

Ingredients:

4 cups thinly sliced ​​potatoes
3 tablespoons butter
1 1/2 cups milk
3 tablespoons all-purpose flour
1 cup shredded sharp cheddar cheese
½ cup shredded cheese (cheddar or gruyere) for garnish
Salt to taste
Optional: 1/ 2 cup sliced ​​green onions, pinch of cayenne pepper
Instructions:

Preheat the oven to 190°C (375°F) and grease a baking tray.

Melt the butter in a saucepan over medium heat. Stir in the flour and cook for 1 to 2 minutes until golden brown.

Add the milk little by little, stirring constantly, and cook until the sauce has thickened.