Snap off tough ends of asparagus. Bring 4 quarts water to a boil in an 8-quart stockpot. Add half of asparagus; cook 3 minutes. Remove asparagus from stockpot. Rinse with cold water; drain and pat dry. Repeat procedure with remaining asparagus.
Combine the Dijon mustard, lemon juice, and salt in a small bowl. Place a large nonstick skillet over medium heat until hot. Add mustard seeds; cook 1 minute, stirring constantly. Add asparagus and mustard mixture, and cook 2 minutes or until thoroughly heated.