01 - Heat olive oil in a large soup pot over medium heat. Add the sausage, breaking it into crumbles with a wooden spoon. Cook until evenly browned, approximately 5 minutes. Transfer the sausage to a plate and set aside.
02 - In the same pot, cook the diced onion until translucent, about 3 to 4 minutes. Add the minced garlic and stir for 1 minute until fragrant.
03 - Add the sliced potatoes and chicken broth to the pot. Bring to a boil, then reduce the heat and simmer uncovered for 12 to 15 minutes until the potatoes are just tender when pierced with a fork.
04 - Stir in the chopped kale and the reserved browned sausage. Simmer for an additional 5 minutes until the kale has wilted and the flavors meld together.
05 - Reduce the heat to low. Pour in the heavy cream and stir gently to combine. Season with crushed red pepper flakes, salt, and black pepper to taste. Heat through without bringing to a boil.
06 - Ladle the soup into warm bowls. Garnish with grated Parmesan cheese if desired and serve immediately with crusty bread alongside.