ingredients2 pounds beef round steak cut into 1-in divided, plus more as needed 1 medium sized onion chopped 2 cloves garlic mincedâ  2 tablespoons tomato paste 1 1/2 cups beef broth 1 tablespoon butter 12 ounces mushrooms sliced 2 tablespoons cornstarch 3 tablespoons cold water 1/3 cup sour cream cooked eg