Melt 2 tablespoons butter in a saucepan over medium heat
Add 2 tablespoons all-purpose flour
Whisk constantly for 1 to 2 minutes to form a smooth roux
Slowly pour in 2 cups warm milk while whisking continuously
Keep whisking until the sauce is smooth and begins to thicken
Cook for 3 to 5 minutes, stirring often, until the sauce coats the back of a spoon
Season with salt, white pepper, and a pinch of nutmeg if desired
Remove from heat and use immediately