1.Combine ground beef, egg, garlic, ½ cup cilantro, 1 teaspoon cumin, 1 teaspoon salt, ¼ teaspoon pepper, and cooked rice. Form 25 tight meatballs by rolling between your palms, about 1½ inches wide.
2.In the soup pot add olive oil and turn the burner onto medium heat. In two batches brown meatballs on both sides then transfer to a plate. Repeat with second batch then set aside. Pour out the oil from the pot except 1 tablespoon.
3.Add carrot, celery, and potatoes then season with 1/2 teaspoon salt and 1/4 teaspoon pepper. Scrape up the brown bits and saute for a few minutes until vegetables are softened.
4.Add chicken broth, diced tomatoes, ½ teaspoon cumin, and oregano. Bring to a boil, and reduce heat to a simmer for 10 minutes.
5.Add meatballs and their juices to the soup and simmer for another 20 minutes. Add 1/2 cup of cilantro and mix well. Additional salt and pepper to taste, if needed. Enjoy immediately.