Stir together: vinegar, oil, and dijon mustard in a large bowl. Set aside while cooking asparagus.
In a large, deep skillet heat 2 inches of water and half of the salt to boiling.
Break or slice off the lower stems of the asparagus spears. Rinse and place half the spears in boiling water.
Cover and cook 5 to 6 minutes, or just until tender crisp. Repeat with remaining asparagus spears. Toss gently until spears are evenly coated. Arrange asparagus spears on serving plate. Sprinkle evenly with parmesan cheese.