Cut meat across the grain into ½-inch strips, about 1 ½ inches long.
Melt butter in large skillet. Add mushrooms and onion; cook and stir until onion is tender, then remove from skillet.
In same skillet, cook meat until light brown.
Reserve ¼ cup of the broth, stir in remaining broth, the catsup, garlic and salt. Cover; simmer 15 minutes.
Blend reserved broth and flour, stir into meat mixture. Add mushrooms and onion.
Heat to boiling, stirring constantly. Boil and stir 1 minute.
Reduce heat. Stir in sour cream; heat.
Serve over noodles.