Tortellini Soup with Italian Sausage

Heat a large pot over medium-high heat. Add the sausage, onions, and garlic and cook, breaking up the meat with a wooden spoon, until it is browned and the onion is translucent, about 5 minutes. Drain off any excessive fat. Whisk in the chicken stock, crushed tomatoes, and tomato paste until fully incorporated. Bring to a boil and add the salt, then reduce the heat to a simmer and cook until slightly reduced, about 15 minutes. Stir in the kale, tortellini, and cream. Cook until the kale is wilted and the pasta is tender, 3-5 minutes. Ladle the soup into bowls. Sprinkle with Parmesan and red pepper flakes, if desired, before serving.