Heat the olive oil in a large pot over medium heat.
Add the chopped onion and sauté until translucent, about 5 minutes.
Stir in the minced garlic and cook for an additional minute.
Add the Italian sausage, breaking it apart with a spoon as it cooks.
Pour in the chicken broth and bring to a boil.
Stir in the kale and cook until wilted, about 3-4 minutes.
Reduce heat to low and stir in the heavy cream and Parmesan cheese.
Add red pepper flakes, salt, and pepper to taste.
Serve hot, garnished with additional Parmesan if desired.