Brown the sausage: Heat olive oil in a large Dutch oven or heavy soup pot over medium-high heat. Add the Italian sausage, breaking it up into bite-sized crumbles with a wooden spoon, until browned and cooked through, about 5 to 6 minutes. Drain excess grease if needed, leaving 1 tablespoon in the pot for rich flavor.

Sauté aromatics: Add the diced onion to the pot with the sausage and cook for 3 to 4 minutes until translucent. Stir in minced garlic and tomato paste, cooking for 1 minute until fragrant and deep brick-red.

Simmer broth: Pour in the chicken broth and crushed tomatoes. Season with Italian seasoning, red pepper flakes, kosher salt, and black pepper. Bring the soup to a gentle boil, then reduce heat to medium-low and simmer uncovered for 10 minutes to allow flavors to meld.

Cook tortellini: Increase heat slightly to a gentle simmer and add the refrigerated cheese tortellini. Cook according to package directions, about 3 to 4 minutes, until tender and floating.

Finish with cream and spinach: Reduce heat to low. Stir in the heavy cream, fresh baby spinach, and grated Parmesan cheese. Stir continuously for 1 to 2 minutes until the spinach is gently wilted and the cheese has melted into the broth.

Garnish and serve: Ladle into warm soup bowls. Crown with extra grated Parmesan, fresh cracked pepper, and chopped basil. Serve immediately with warm crusty garlic bread!