01 - Heat olive oil in a large soup pot over medium heat. Add the Italian sausage, breaking it into small crumbles with a wooden spoon. Cook until evenly browned and no longer pink, approximately 5 minutes. Transfer the sausage to a plate using a slotted spoon and set aside, leaving the rendered fat in the pot.
02 - In the same pot with the residual drippings, add the diced onion and cook, stirring occasionally, until softened and translucent, about 3 to 4 minutes. Add the minced garlic and continue cooking for 1 minute until fragrant, being careful not to let it brown.
03 - Add the sliced potatoes and chicken broth to the pot. Bring to a rolling boil over medium-high heat, 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 - Return the browned sausage to the pot and add the chopped kale. Stir to combine and simmer for an additional 5 minutes, allowing the kale to wilt and the flavors to meld together.
05 - Reduce the heat to low. Slowly stir in the heavy cream and add the crushed red pepper flakes, salt, and black pepper to taste. Heat the soup through gently, making sure not to bring it to a boil, which could cause the cream to separate.
06 - Ladle the hot soup into serving bowls. Garnish each portion with grated Parmesan cheese if desired, and serve immediately alongside crusty bread for dipping.