Here is the basic white sauce used for layering lasagne, covering cannelloni, and making casseroles in general. This recipe makes enough for a large (12 to 14 servings) lasagne, and is of medium consistency, a factor controlled by adding more or less flour as you wish.

8 tbsp. unsalted butter
3/4 c. quick-mixing flour
4 c. milk
1/2 tsp. freshly grated nutmeg
1/2 tsp. salt
Freshly ground pepper to taste

Melt the butter in a heavy saucepan over low heat. Add the flour all at once, and stir rapidly with a wire whisk until blended. When you use the quick mixing flour that has a granular feeling, lumps never form. With ordinary flour, lumps are a good possibility.

Heat the milk to scalding (just under a boil, when a skin has formed on the top), and add it all at once to the butter-flour mixture, stirring vigorously with a whisk. Continue cooking over medium heat, stirring constantly, until the sauce has thickened and is smooth, about the consistency of a thin pudding. Add the nutmeg, salt, and a few grinds of pepper.

Cool the sauce for about 15 minutes before using. It becomes firmer as it cools.