Mix all the meatball ingredients together with your hands or a fork. Form into bite size meatballs. The original recipe called for the meatballs to be cooked in the soup. I like to bake mine in the oven for 25 minutes, turning once. If you cook them in the oven, be sure to cook on a surface coated with non-stick cooking spray or on non stick foil, otherwise they will stick to the pan.
Meanwhile, add oil to a medium 4 qt stock pot. Saute the onions for 3 minutes. Add the garlic and saute another minute. Add the beef broth. Stir.
Add meatballs, stewed tomatoes, chipotle peppers and bay leaf to the beef broth. Bring to a boil, reduce heat and simmer covered for 30 minutes, stirring at 10 minute intervals.
Serve topped with cheddar cheese and cilantro and chunks of fresh avocado.