White sauce, or béchamel, is made with a mixture of butter and flour (called a roux) that is then cooked on low heat with milk, while stirring constantly. The quantity of butter and flour must be the same, and the amount of milk you add depends on how thick or thin you want the sauce to be. Once it’s thickened to your desired consistency, add salt and pepper. Feel free to add a pinch of nutmeg too.
Use this sauce in lasagna or casseroles, and try adding it to grilled cheese to make the famous French ‘croque-monsieur’.