To make this recipe on the stovetop, melt two tablespoons of butter in a large skillet over medium heat. Add mushrooms and onions, and sauté until soft, 4-5 minutes. Add the meatballs, beef broth, Worcestershire sauce, garlic, and spices and simmer over medium-low heat for 20 minutes. Stir in the sour cream and cook an additional 5 minutes.