1. Meatballs: In a large bowl, combine beef, egg, bread crumbs, mint, parsley, garlic, lemon zest, salt and black pepper. Stir to mix well. Using your hands or a small scoop, shape the mixture into about 36 meatballs using about 1 heaping tablespoon for each.

2. Soup: Heat the oil in a large pot over medium heat. Add leeks and celery and cook 5 minutes, stirring often, until softened.

3. Stir in the broth, tomatoes and escarole and bring to a boil. Stir in the orzo and return to a boil. Carefully drop in the meatballs and return to a boil.

4. Reduce the heat to medium-low, cover, and cook about 18 minutes, stirring occasionally, until the orzo is tender and the meatballs are cooked through. Stir in lemon juice and hot pepper sauce.