Versatile basic white sauce is an essential French sauce used in various dishes. It's a sauce you'll use to make macaroni and cheese, lasagna, croquettes, and gratins.
Melt the butter in a small saucepan over low heat.
When the butter begins to bubble, whisk in the flour and add the 1/4 teaspoon of kosher salt and a dash of freshly ground black pepper along with the nutmeg, if using.
Increase the heat to medium-low and cook the roux while whisking constantly for 2 minutes.
Increase the heat to medium and gradually whisk in the milk.
Continue cooking until the sauce is thickened and bubbling.