In a large bowl, combine ground beef, egg, bread crumbs, milk and 1/4 tsp. each salt and pepper.  Form into 16 meatballs.



Heat a large nonstick skillet over medium-high heat; coat with nonstick cooking spray.  Add onion and cook 2 minutes.  Combine broth and four; add to skillet.  Brint to a simmer.  Add mushrooms, meatballs and remaining 1/4 tsp. each salt and pepper.  Cook 12 minutes, turning meatballs once, until temperature reaches 160 degrees.  Stir in souor cream and dill off heat.



Serve with noodles and, if desired, broccoli.