Coat beef strips with 1 tbsp. flour and salt. Brown beef strips quickly in1 tbsp. butter in a skillet. Add mushrooms, onion and garlic; cook untilonion 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 tomatopaste. Stir in broth. Stir over medium heat until thick and bubbly.
Return meat and mushrooms to skillet. Stir in sour cream; cook slowlyuntil heated through. Do not boil. Serve over hot buttered noodles.