01 - Heat olive oil in a large soup pot or Dutch oven over medium heat. Add the sausage, breaking it apart with a wooden spoon, and cook 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, rosemary, salt, black pepper, and 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 the mixture to a boil. Reduce the heat to a gentle 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, warm the heavy cream in a small saucepan over low heat. Add the Parmesan, ricotta, chopped sage, salt, and pepper. 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. Top with butter-fried sage leaves and a generous crack of black pepper if desired. Serve immediately.