1. 1. Brown the Sausage and Saute Aromatics: In a large skillet over medium-high heat, cook the ground Italian sausage, breaking it up with a spoon, until it’s no longer pink. Drain off any excess grease. Add the chopped onion to the skillet and cook until softened, about 5-7 minutes. Stir in the minced garlic and cook for another minute until fragrant. This initial browning step is crucial for developing deep flavors.

2. 2. Combine Ingredients in the Slow Cooker: Transfer the cooked sausage, onion, and garlic mixture to your slow cooker. Add the crushed tomatoes, diced tomatoes (undrained), chicken broth, dried basil, dried oregano, and red pepper flakes (if using). Stir everything together until well combined.

3. 3. Slow Cook to Perfection: Cover the slow cooker and cook on low for 6-8 hours or on high for 3-4 hours. The longer cooking time allows the flavors to meld beautifully and the tomatoes to break down, creating a rich base for the soup.

4. 4. Add Cream and Tortellini: About 20-30 minutes before you’re ready to serve, stir in the heavy cream and the refrigerated cheese tortellini. The tortellini will cook quickly in the hot broth. Keep an eye on it to prevent overcooking, as you want it tender but still holding its shape.

5. 5. Stir in Fresh Spinach: Once the tortellini is cooked through, add the fresh spinach to the slow cooker. Stir gently until the spinach wilts, which usually takes just a couple of minutes. The residual heat from the soup will be enough to cook it perfectly.

6. 6. Season and Serve: Taste the soup and season with salt and black pepper as needed. Ladle the hot soup into bowls and garnish generously with freshly grated Parmesan cheese before serving. A sprinkle of fresh parsley can also add a nice touch of color.