Step 1: Brown the Sausage and Bacon
In a large Dutch oven or heavy-bottomed stockpot, cook the chopped bacon (if using) over medium heat until crispy. Remove the bacon with a slotted spoon and set it aside on a paper towel, leaving the rendered fat in the pot. Add the Italian sausage to the pot, breaking it up with a wooden spoon. Cook until it is well-browned and no longer pink. This step builds the foundational, savory flavor of the entire soup.

Step 2: Sauté the Aromatics
Add the diced onion to the pot with the sausage and cook for 5-6 minutes, until it becomes softened and translucent. Add the minced garlic and cook for an additional minute until fragrant. Be careful not to burn the garlic. If there is excess grease, you can drain off all but about 1 tablespoon.

Step 3: Build the Broth Base
Pour the chicken broth and water into the pot, scraping the bottom with your spoon to lift all the delicious browned bits (fond). This process, called deglazing, is crucial for flavor. Add the cubed potatoes, dried oregano, and red pepper flakes (if using). Bring the soup to a boil, then reduce the heat to a simmer.

Step 4: Simmer Until Potatoes are Tender
Cover the pot and let the soup simmer for 15-20 minutes, or until the potatoes are fork-tender. They should be soft but not falling apart completely.

Step 5: Thicken the Soup (Optional but Recommended)
If you prefer a thicker, more stew-like consistency, this is the time to thicken the soup. In a small bowl, create a slurry by mixing the 2 tablespoons of flour with a few tablespoons of the hot soup broth until smooth. Slowly whisk this slurry back into the simmering soup. Alternatively, you can use a cornstarch slurry. Let the soup simmer for another 3-5 minutes until it thickens slightly.

Step 6: Wilt the Kale and Add Cream
Stir in the chopped kale and let it cook for 3-5 minutes, just until it has wilted and turned bright green. Then, turn the heat down to low. Stir in the heavy cream. It is critical not to let the soup boil after adding the cream, as this can cause it to curdle. Heat it through gently until just steaming.

Step 7: Final Seasoning and Serve
Taste the soup and season with salt and freshly ground black pepper as needed. The sausage and bacon are salty, so taste first. Ladle the hot soup into bowls and garnish with the reserved crispy bacon, a generous sprinkle of freshly grated Parmesan cheese, and a pinch of fresh parsley.