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 throughout, approximately 5 minutes. Transfer the browned sausage to a plate and set aside.
02 - In the same pot, cook the diced onion over medium heat until soft and translucent, 3 to 4 minutes. Add the minced garlic and stir continuously for 1 minute until fragrant.
03 - Add the sliced potatoes and chicken broth to the pot. Bring to a rolling boil, then reduce the heat to maintain a gentle simmer. Cook uncovered for 12 to 15 minutes until the potatoes are fork-tender.
04 - Return the browned sausage to the pot along with the chopped kale. Simmer for an additional 5 minutes until the kale has wilted and the flavors meld together.
05 - Reduce the heat to low and stir in the heavy cream. Season with crushed red pepper flakes, salt, and black pepper to taste. Gently heat through without bringing to a boil to prevent the cream from separating.
06 - Ladle the soup into warmed bowls and garnish with grated Parmesan cheese if desired. Serve immediately alongside crusty bread.