Béchamel Sauce

Heat milk in a saucepan to simmering (just below boiling point). You can season the milk with salt, white pepper, and nutmeg to make incorporation easier later on.

Make the roux: In a separate saucepan, melt the butter over medium heat. Add the flour a little at a time, mixing continually, to make a very blond roux. Cook for 5-7 minutes. You don't want a brown/gumbo roux.

Using a ladle or coffee cup, slowly incorporate the hot milk into the roux:

When you add the first portion of milk, the roux will become even more viscous and stiff. This is natural. As you continue adding milk, it will return to a semi-liquid stage, then a liquid stage.

Once all the milk is incorporated, keep the thinned sauce over heat and stir continually until the boiling of the sauce causes it to re-thicken into a final Béchamel sauce.

For a final touch, add a handful of grated Parmesan (and/or the other cheeses listed) and incorporate fully into the sauce. This step is especially important for Italian recipes like white lasagna or Alfredo sauce.