Heat the olive oil in a large pot over medium heat. Sprinkle in the crushed red pepper flakes and let them cook briefly to release their flavors.

Add the spicy Italian sausage to the pot, breaking it apart as it cooks until it is browned throughout. Remove and set aside once done.

In the same pot, mix in your chopped onion, celery, and carrot. Sauté these until softened, which should take about 5 to 7 minutes.

Stir in the minced garlic and sauté for an additional 30 to 60 seconds until it's aromatic.

If using, mix in the tomato paste at this stage.

Pour in the chicken stock along with the diced tomatoes. Season with Italian herbs, salt, and black pepper, and bring everything to a rolling boil.

Once boiling, introduce the tortellini and cook according to package directions, generally taking 3 to 7 minutes.

Reduce the heat and gently fold in the heavy cream and parmesan cheese until well blended.

Add in the chopped kale and let the soup simmer for a few additional minutes for flavors to meld.

Finally, taste your soup and adjust seasonings as preferred. Serve hot with additional parmesan on top.