01 - Heat olive oil in a large soup pot over medium heat. Add the sausage, breaking it into crumbles with a wooden spoon, and cook until evenly browned, about 5 minutes. Transfer the sausage to a plate and set aside.
02 - In the same pot, cook the diced onion over medium heat until translucent, 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 fork-tender.
04 - Stir in the chopped kale and the reserved browned sausage. Simmer for an additional 5 minutes until the kale has wilted and softened.
05 - Reduce the heat to low and stir in the heavy cream. Season with red pepper flakes, salt, and black pepper to taste. Heat through gently without bringing to a boil.
06 - Ladle into bowls and garnish with grated Parmesan cheese if desired. Serve with crusty bread alongside.