In a saucepan over low heat, melt 2 tablespoons of butter. Be sure not to let the butter burn or turn brown, as this will affect the color and taste of the sauce.

Once the butter is melted, add 2 tablespoons of all-purpose flour to the pan. Whisk the mixture until the flour is fully combined with the butter, and no lumps remain.

Continue whisking the mixture for 2-3 minutes, or until the roux turns slightly golden in color. This will help to cook out the raw flour taste and give the sauce a nutty flavor.

Slowly pour 1 cup of milk into the roux, whisking constantly to prevent any lumps from forming. You can use whole milk or a combination of milk and cream for a richer sauce. Continue whisking until the mixture is smooth and creamy.

Increase the heat to medium and bring the sauce to a gentle simmer. Stir the sauce occasionally to prevent it from sticking to the bottom of the pan. Season the sauce with salt, pepper, and nutmeg to taste. You can also add other herbs or spices at this point, depending on the flavor profile you want to create.

Simmer the sauce for 10-15 minutes, or until it reaches your desired thickness. If the sauce becomes too thick, you can add a little more milk to thin it out.