Take out any grease. Don't wash. Add 2 Tablespoons butter to the pan and stir in your sliced onion. On medium heat, cook for 5-10 minutes. The onions will turn golden brown and become tender and fragrant. Add mushrooms. Cook for another few minutes. Turn down the heat to medium, and then add in the beef stock, Worcestershire sauce, and ketchup. Stir, and let simmer for 10 minutes. Mix in your Kitchen Bouquet. Mix well. Gravy will thicken. Salt and pepper to taste. The meatballs should be returned to the gravy. Turn heat down and cover the skillet. Cover the skillet with gravy and cook meatballs for 20-30 minutes. These will tenderize them, so be careful when stirring.