1. Heat olive oil in large pot over medium heat. Add sausage and cook, breaking up with the back of a spoon until browned, about 5 min. Add onions and cook until softened, about 6 min. Add garlic, oregano and red pepper flakes and cook 1 min. more. Add tomato paste and cook, stirring another 3-4 min. or until the tomato paste turns a rusty brown color.
2. Add diced tomatoes, bay leaves and chicken stock and stir to combine. Bring to a boil, reduce heat, and simmer about 30 min. Add pasta and cook for about 8 min. or until al dente. Stir in basil and season to taste with salt and black pepper.
3. In small bowl, combine ricotta, Parmesan cheese, salt and pepper.
4. To serve, place a dollop of ricotta cheese mixture in each soup bowl; sprinkle some of the mozzarella on top and ladle the hot soup over the cheese. Serve hot.
Recipe excerpted from "300 Sensational Soups" by Carla Snyder and Meredith Deeds. ©Robert Rose Inc. Reprinted with permission. All rights reserved.