Heat the olive oil in a large Dutch oven over medium heat. Add the sausage, with casings removed, and stir with a heavy spoon to break the meat into crumbles.
Add the onion, crushed red pepper flakes, oregano, and crushed fennel seeds, then cook for 3-4 minutes or until the meat is cooked through and the onions are softened.
Add the garlic and cook, stirring constantly, for 1 minute. Add the diced tomatoes, chicken broth, and bay leaf, then season with sea salt and freshly cracked pepper, to taste. Cover and simmer for an hour.
Cook the pasta per instructions, then drain and set aside until right before serving.
Combine the ricotta cheese, Parmesan cheese, and 1/2 tbsp of basil in a bowl, then season with a bit of sea salt and freshly cracked pepper, to taste. Set aside.
Once the soup has simmered for an hour, taste it and re-season it if needed. Add the cooked pasta, spinach, and remaining basil to the soup.
Ladle the soup into bowls, then top with a dollop of the ricotta mixture. Serve immediately. Enjoy.