In a wide frying pan, bring 1 1/2 inches water to a boil over high heat.
Add asparagus; reduce heat, cover, and boil gently just until tender when pierced 5 to 7 minutes.
Drain, place on a warm platter, and keep warm.
Melt 1 tablespoon of the butter in a 1- to 2-quart pan over medium heat.
Add shallots and cook, stirring, for 1 minute.
Add mustard and orange juice, increase heat to high, and bring to a boil; boil until reduced to 2/3cup about 5 minutes.
Reduce heat to low, add remaining 7 tablespoons butter all at once, and cook, stirring constantly, until butter is smoothly blended into sauce.
Season to taste with salt and pepper.
Spoon sauce over asparagus; garnish with orange slices or orange peel, if desired.