Coat beef strips with 1 tbsp. flour and salt. Brown beef strips quickly in 1 tbsp. butter in a skillet. Add mushrooms, onion and garlic; cook until onion is crisp-tender, 3 to 4 min. Remove meat and mushrooms from pan. Add 2 tbsp. butter to pan drippings; blend in 3 tbsp. flour. Add tomato paste. Stir in broth. Stir over medium heat until thick and bubbly. Return meat and mushrooms to skillet. Stir in sour cream; cook slowly until heated through. Do not boil. Serve over hot buttered noodles. Makes 4-5 servings.