Spray 3 1/2- to 4-quart slow cooker with cooking spray. In medium bowl, mix turkey, bread crumbs, onion, mustard, salt and pepper. Shape mixture into 16 meatballs. Spray 12-inch nonstick skillet with cooking spray. Add meatballs; cook over medium-high heat until brown. Place meatballs in slow cooker; top with mushrooms. Add broth.
Cover; cook on Low heat setting 6 to 7 hours.
Cook and drain noodles as directed on package. Remove meatballs and mushrooms from slow cooker, using slotted spoon; cover to keep warm. In small bowl, mix flour and water; gradually stir into slow cooker until blended. Increase heat setting to High. Cover; cook 15 to 20 minutes or until thickened. Stir in dip; heat until hot. Stir in meatballs and mushrooms. Serve over noodles. Garnish with parsley.