01 - Heat olive oil in a large soup pot over medium heat. Add the sausage, breaking it apart with a wooden spoon into small crumbles. Cook until evenly browned and no longer pink, approximately 5 minutes. Transfer the browned sausage to a plate lined with paper towels and set aside.
02 - In the same pot with the rendered drippings, add the diced onion and cook, stirring occasionally, until soft and translucent, about 3 to 4 minutes. Add the minced garlic and stir continuously for 1 minute until fragrant.
03 - Add the thinly sliced potatoes and chicken broth to the pot. Bring the liquid to a rolling boil, then reduce the heat to medium-low. Simmer uncovered for 12 to 15 minutes, or until the potatoes are fork-tender but not falling apart.
04 - Stir the chopped kale and the reserved browned sausage into the pot. Continue simmering for an additional 5 minutes until the kale has wilted and the sausage is heated through.
05 - Reduce the heat to low. Pour in the heavy cream and stir gently to combine. Season with crushed red pepper flakes, kosher salt, and freshly ground black pepper to taste. Allow the soup to warm through gently, but do not bring to a boil after adding the cream.
06 - Ladle the hot soup into serving bowls. Garnish each portion with grated Parmesan cheese if desired. Serve immediately alongside crusty bread.