Mix the onion, minced meat and egg together and season with salt, pepper and Worcestershire sauce. Shape the mixture into balls, fry them all over in oil, then remove them.
Braise the tomatoes and onions in the oil.
Stir in the beans with the peppers and bell pepper. Cook the whole thing for about 9 minutes. Season with salt, chili powder, mustard and tomato ketchup. Add the balls again and sprinkle everything with parsley.