01 - Heat olive oil in a large soup pot or Dutch oven over medium heat. Add the sausage with casings removed and cook, breaking it apart with a spoon, for 5 to 6 minutes until evenly browned. Transfer the sausage to a plate and set aside, leaving any rendered drippings in the pot.
02 - Add the diced onion, carrots, and celery to the pot. Sauté for 4 to 5 minutes until the vegetables are softened. Stir in the minced garlic and cook for 1 minute until fragrant.
03 - Add the cubed butternut squash to the pot. Sprinkle with dried thyme, dried rosemary, salt, black pepper, and crushed red pepper flakes if using. Stir to coat evenly and cook for 2 minutes to bloom the spices.
04 - Pour in the chicken broth and bring to a boil. Reduce heat to a simmer, cover the pot, and cook for 15 to 20 minutes until the squash is fork-tender.
05 - Use an immersion blender to partially puree the soup directly in the pot, leaving about half of the vegetables intact for a chunky texture. Alternatively, transfer half the soup to a standard blender, puree until smooth, and return it to the pot.
06 - Return the browned sausage to the pot and bring the soup back to a gentle simmer. Add the cheese tortellini and cook according to package instructions, typically 5 to 7 minutes, until the pasta is tender and floats to the surface.
07 - While the soup simmers, combine the heavy cream, Parmesan cheese, ricotta cheese, chopped fresh sage, and a pinch of salt and pepper in a small saucepan over low heat. Stir gently for 2 to 3 minutes until the cheeses are melted and the mixture is smooth and fragrant.
08 - Ladle the hot soup into serving bowls. Drizzle 1 to 2 tablespoons of the sage cheese swirl over each portion. Garnish with fried sage leaves and freshly ground black pepper if desired. Serve immediately.