In a large bowl, combine the egg, crumbs, milk, mustard, salt and pepper. Crumble beef over mixture. Shape into 1-in. balls. In a Dutch oven over medium heat, brown meatballs in oil; drain and set aside.
In same pan, sauté onion and garlic in oil until onion is tender. Whisk in flour. Gradually add broth, stirring constantly; bring to a boil. Cook and stir 1-2 minutes or until thickened. Stir in the tomatoes, paste, bay leaf, thyme and salt. Add meatballs and carrots; bring to a boil. Reduce heat; cover and simmer 30 minutes.
Add zucchini and peppers; bring to a boil. Reduce heat; cover and simmer 10-15 minutes or until vegetables are tender. Add parsley and pasta; heat through. Remove bay leaf. Yield: 6-8 servings.