Heat oil in a large nonstick skillet over medium-high heat; add turkey. Sauté 6 minutes or until browned. Remove turkey from skillet, and set aside.
Add onion to skillet; sauté 8 minutes. Add mushrooms; sauté 3 minutes or until tender. Add water, mustard, and broth; stir well. Return turkey to skillet, and bring to a boil. Cover, reduce heat, and simmer 20 minutes.
Cook noodles in boiling water 8 minutes or until tender. Drain; set aside.
Combine milk, flour, and pepper, stirring with a whisk. Add to turkey mixture. Simmer 2 minutes or until thick, stirring constantly. Serve turkey and gravy over noodles; garnish with parsley, if desired.