Place butter in 4-cup glass measure and cook on HI, 1 minute.
Stir flour into butter until smooth.
Whisk in milk, pepper, and nutmeg, blending well.
Cook on HI, 3 minutes, stirring once.
At Pause, whisk until smooth.
Cook on HI, 1 1/2 to 2 minutes, or until thickened.
Serve with cooked broccoli or cauliflower.