01 - Heat olive oil in a large soup pot over medium heat. Add the sausage, breaking it into small crumbles with a wooden spoon. Cook until evenly browned throughout, approximately 5 minutes. Transfer the browned sausage to a plate and set aside, leaving any rendered drippings in the pot.
02 - In the same pot with the residual drippings, add the diced onion and cook over medium heat until softened 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 the liquid to a rolling boil, then immediately reduce the heat to medium-low. Simmer uncovered for 12 to 15 minutes, or until the potatoes are fork-tender.
04 - Return the browned sausage to the pot along with the chopped kale. Stir to combine and continue simmering for an additional 5 minutes until the kale has wilted and the flavors meld together.
05 - Reduce the heat to low. Slowly stir in the heavy cream, crushed red pepper flakes, salt, and black pepper. Gently heat the soup through without bringing it to a boil, which could cause the cream to separate.
06 - Ladle the finished soup into warmed bowls. Garnish each serving with a generous sprinkle of grated Parmesan cheese. Serve immediately alongside crusty bread if desired.