Do this
Melt butter on low heat. Stir in the same weight of flour. Keep stirring until it smells nutty and looks light brown.
Why it works
Toasting cooks off the raw flour taste. It also adds a nutty, baked aroma. The fat keeps the flour from clumping later.
When to skip it
Skip toasting for a white sauce. There you want a pale color and the most thickness.
