Spray 12-inch nonstick skillet with nonstick cooking spray. Add chicken; sprinkle with garlic-pepper blend. Cook over medium-high heat until browned, stirring occasionally.
Add broth and gravy; mix well. Bring to a boil. Stir in noodles and mushrooms. Return to a boil. Reduce heat to medium-low; cover and simmer 10 to 15 minutes or until noodles are tender and chicken is no longer pink in center, stirring occasionally.
Stir in sour cream and ketchup until well blended. Sprinkle individual servings with onions.