Heat the olive oil in a large Dutch oven or stock pot over medium heat. Cook the onion until soft and translucent, 3 to 4 minutes.
1 Tablespoon olive oil or avocado oil, 1 small yellow onion
Add the Italian sausage and cook, breaking it into small pieces, until browned and cooked through. Stir in the garlic and cook until fragrant, 1 minute.
1 lb hot or regular Italian sausage, 3 cloves garlic
Stir in the Italian seasoning, salt, red pepper flakes, and tomato paste. Cook for 1 to 2 minutes, stirring frequently, until the tomato paste darkens slightly and begins to caramelize on the bottom of the pot.
2 teaspoons Italian seasoning, 1 teaspoon kosher salt, 1/2 teaspoon crushed red pepper flakes, 3 Tablespoons tomato paste
Pour in the crushed tomatoes and broth, scraping up any brown bits from the bottom of the pot. Bring to a boil over medium high heat, then reduce the heat to medium low and simmer for 5 to 10 minutes.
1 15 oz can crushed tomatoes, 4 cups reduced sodium chicken broth
Add the tortellini and simmer according to package directions, usually 3 to 4 minutes, until just tender.
14 to 16 oz refrigerated cheese tortellini
Reduce the heat to low. Stir in the parmesan cheese, kale, and cream, and cook for 1 to 2 minutes, until the kale is wilted and the soup is creamy. Taste and adjust salt or red pepper flakes as needed.
1/2 cup freshly grated parmesan cheese, 4 cups kale, 1/2 cup heavy cream
Whisk the cornstarch with 1 Tablespoon of cold water until smooth. Stir the slurry into the soup and simmer gently for 1 to 2 minutes until thickened. Add a second batch of slurry if you prefer a thicker soup.
1 Tablespoon cornstarch
Ladle into bowls and top with parmesan cheese and parsley.
Parmesan cheese and parsley