In a large bowl combine 1/2 cup yogurt and bread crumbs; let stand 5 minutes.
Add ground beef, egg, onion and salt.
Mix well and shape into 1 1/4 inch meatballs.
Spray a large nonstick skillet with vegetable cooking spray.
Cook meatballs over medium heat until brown and cooked through, turning often; drain.
Wipe skillet dry.
In a small bowl combine 1 cup yogurt, flour, beef broth mix and Worcestershire sauce until smooth.
Add to skillet.
Cook over medium-low heat, stirring constantly, until thickened.
Do not boil.
Reduce heat to low.
Add meatballs; mix with sauce and cook until just heated through.
If desired, garnish with parsley.