Escarole Soup with Turkey Meatballs

Name: Escarole Soup with Turkey Meatballs
Ingredients: 1 pound ground turkey; 2 eggs, beaten to mix; 1 clove garlic, minced; 1 small onion, minced; 1/2 cup dry bread crumbs; 1/2 cup grated Parmesan; 1/2 cup chopped fresh parsley; 1 1/2 teaspoons salt; 1/4 teaspoon fresh-ground black pepper; 3 tablespoons olive oil; 1/2 head escarole (about 1/2 pound), leaves washed well and chopped (about 1 quart); 1 1/2 quarts canned low-sodium chicken broth or homemade stock; 2 cups water; 2 tablespoons red- or white-wine vinegar; 1/4 teaspoon red-pepper flakes