Combine first 6 ingredients in a bowl. Stir well; set aside.
Steam asparagus, covered, 3 minutes or until crisp-tender; set aside.
Brush 2 teaspoons mustard over both sides of chicken; sprinkle chicken with 1/4 teaspoon salt and 1/8 teaspoon pepper. Cut chicken across the grain into thin slices. Heat 1 teaspoon oil in a large nonstick skillet coated with cooking spray over medium-high heat, and add chicken and green onions. Sauté 6 minutes or until chicken is done. Add vinegar mixture to skillet, and cook 1 minute, stirring constantly.
Arrange 1 1/2 cups salad greens on 4 plates; top with 1/2 cup asparagus. Divide chicken mixture evenly among salads.