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