| 1. | In a large bowl combine the flour, salt and pepper. Toss the beef strips in the mixture until they are coated. Shake off any excess flour. Put the strips aside. |
| 2. | Heat the butter in a large, heavy frying pan over moderately high heat until bubbly. Add half the meat and cook, stirring once or twice, for 1 – 2 minutes or until no pink remains. Transfer the cooked meat to a plate. Cook the remaining meat in the same way and add to the plate. |
| 3. | Reduce the heat to moderately low. Add the onion and garlic and cook uncovered for 5 minutes, or until the onion is soft. Add the mushrooms, beef stock and tomato paste, raise the heat to high, and cook for 2 minutes, scraping up any brown bits stuck to the pan. |
| 4. | Return the meat and any accumulated juices to the pan and heat through – about 1 minute. Remove the pan from the heat and stir in the sour cream (or yogurt). Serve immediately over buttered noodles or rice, and with a lettuce and tomato salad. |