In a large pot over high heat, add olive oil. Once hot, add sausage. Sear for a minute on each side, then crumble and cook until browned. Remove sausage with a slotted spoon, leaving 1 tablespoon of grease in the pot and draining off the excess.
Reduce heat to medium. Add butter, onions, carrots, and garlic. Season to taste (I add 1/2 teaspoon each of salt & pepper). Sauté until tender, about 7–9 minutes. Sprinkle flour on top and cook for another minute, stirring constantly.
Gradually add 1 cup of broth, whisking constantly to create a slurry. Add the remaining broth slowly, whisking and scraping the bottom of the pot. Add Italian seasoning and red pepper flakes, if using.
Bring broth to a boil, then add pasta. Cook according to package instructions, minus two minutes. Stir occasionally to prevent sticking.
Reduce heat to low. Add cream, kale, and return sausage, stirring well. Add Parmesan gradually, 1/4 cup at a time, to avoid clumping. Stir until melted. Season with salt as needed. Add more broth for a thinner consistency, if desired.
Serve hot with hearty buttered bread on the side.
Video
Notes
Note 1: A good chicken broth makes a huge difference in flavor. I recommend using Swanson®.Note 2: The secret to this soup is the Parm! Always use refrigerated Parmesan—never the shelf-stable kind (it’s not real cheese!). Go for good-quality grated Parmesan with a sandy texture for the best flavor and perfect saltiness.Storage: Store leftovers in an airtight container for 3–4 days. The pasta will keep soaking up liquid, so use a wire skimmer to remove it and store it separately from the broth.