This side dish is quick and easy to make.
Edit 1-18-06: Thank you to the reviewer who pointed out a typo in the recipe. The amount of ground mustard has been corrected to 1 1/2 tsp. Sorry for the confusion.
Steam/boil asparagus until desired tenderness (usually 3-4 mintes); drain and place on serving platter.
Meanwhile, in a small saucepan, over med-low heat, melt butter. Add minced onion and saute for about 5-6 minutes, or until onions are translucent and tender; do not brown butter or burn onions.
Reduce heat to low; add salt, white pepper, and ground superfine mustard. Add light sour cream and stir well. Heat through, about 1-2 minutes. Pour sauce over hot, cooked asparagus and serve.