In a 5-quart Dutch oven, heat butter and oil over medium heat. Add onions, celery, carrots and garlic. Cook over medium heat for 10 minutes, stirring often.
Stir in the broth and potatoes. Bring to boiling; reduce heat. Simmer, covered, for 20 minutes. Add tomato puree and Basil Meatballs* to the soup, a few at a time and cook, covered, 10 to 15 minutes more or until no pink remains in meatballs. Season to taste with salt and hot pepper sauce, if you like. Skim fat and garnish each serving with some of the fresh basil. Makes 8 servings.
For a browner meatball, arrange meatballs in a 15x10x1-inch baking pan. Bake, uncovered, in a 350 degree F. oven for 12 to 15 minutes or until no pink remains. Add to soup along with tomato puree and heat through.
In a large bowl, combine egg, bread crumbs, basil, parsley, salt and pepper. Add ground beef. Using two forks, lightly toss together all ingredients. Shape into tiny meatballs. (If you like, use a melon baller or small cookie scoop to shape the meatballs.) Makes 42 (3/4-inch) meatballs.