Heat olive oil in a large pot over medium heat. Add sausage, breaking up into bite sized pieces, and brown for about 5 minutes. Add onions and cook until softened, about 6 minutes. Add garlic, oregano, and red pepper flakes. Cook for 1 minute. Add tomato paste and stir well to incorporate. Cook for 3 to 4 minutes, or until the tomato paste turns a rusty brown color.
Add diced tomatoes, bay leaves, and chicken stock. Stir to combine. Bring to a boil and then reduce heat and simmer for 30 minutes. Add uncooked pasta and cook until al dente. Do not over cook or let soup simmer for a long period of time at this point, as the pasta will get mushy and absorb all the soup broth. You may even want to consider cooking the noodles separately, and then adding some to individual bowls before ladling the soup over them. This would be an especially smart move if you are anticipating any leftovers. Right before serving, stir in the basil and season to taste with salt and freshly ground black pepper.
While the pasta is cooking, prepare the cheesy yum. In a small bowl, combine the ricotta, Parmesan, salt, and pepper.
To serve, place a dollop of the cheesy yum in each soup bowl, sprinkle some of the mozzarella on top and ladle the hot soup over the cheese.
Source: Adapted from 300 Sensational Soups by Carla Snyder and Meredith Deeds, as seen in the February-April 2011 edition of At Home with Kowalski's magazine from Kowalski’s Markets.