Stir onion with garlic, egg, Worcestershire, sage, onion powder, salt and bread crumbs in a medium bowl. Crumble in meat. Using a fork or your hands, gently mix. Form into 6 oval shaped steaks, each about 1/2 in. thick.
Melt 1 tbsp butter in a large non-stick frying pan over medium. When hot, add 3 steaks. Cook until lightly brown on each side, about 3 min per side. Remove to a large plate. Add another 1 tbsp butter to pan and repeat with remaining steaks, then remove to plate.
Add another 1 tbsp butter if pan is dry, then add mushrooms to pan. Cook until soft, about 4 min. Stir in fl our, then gradually add broth. Bring to a boil. Return steaks and any juices to pan. Reduce heat to medium-low, then simmer, covered, until steaks are cooked through, about 5 to 10 min. Sprinkle with parsley, then remove to plates. Serve with egg noodles and green beans.