Heat olive oil in a large soup pot over medium heat.
Add Italian sausage and cook until browned, breaking it apart.
Remove excess grease if necessary and add chopped onion.
Sauté onion until soft, then stir in minced garlic.
Add sliced potatoes and pour in chicken broth.
Bring the soup to a boil, then reduce heat and simmer for 20 minutes.
Stir in heavy cream and chopped kale.
Season with salt, black pepper, and red pepper flakes.
Simmer for 5 more minutes until kale is tender.
Remove from heat and serve hot.