Coat inside of Crockpot™ slow cooker with nonstick cooking spray.
Melt butter in large skillet over medium-high heat. Add onions, half of mushrooms, thyme, ½ teaspoon salt and ¼ teaspoon pepper; cook and stir 3 minutes or until mushrooms have cooked down slightly.
Add remaining mushrooms. Cook 15 minutes or until mushrooms are tender and liquid has almost completely evaporated. Add garlic; cook 2 minutes. Pour in wine; cook and stir 1 minute. Remove to slow cooker.
Stir in broth, Worcestershire sauce and mustard. Cover; cook on HIGH 2 hours or on LOW 4 to 4 ½ hours. Turn off heat. Let cool 10 minutes.
Stir in sour cream, parsley and remaining ¼ teaspoon salt and ¼ teaspoon pepper. Divide noodles evenly among four plates; top with stroganoff to serve.
