Combine first 5 ingredients and 1/4 teaspoon salt in a large bowl; stir well. Shape into 24 (1-inch) balls.
Coat a Dutch oven with cooking spray. Place over medium-high heat until hot. Add meatballs, and cook 8 minutes or until browned, turning often. Remove meatballs from Dutch oven; drain on paper towels. Wipe drippings from Dutch oven with a paper towel.
Add flour to Dutch oven; gradually add beef broth, pepper, and remaining 1/4 teaspoon salt, stirring well with a wire whisk. Bring to a boil; reduce heat, and simmer, stirring constantly, 10 minutes or until mixture is thickened. Stir in noodles, sour cream, and mushrooms. Return meatballs to Dutch oven; cook until thoroughly heated.