Fry up the hot Italian sausage, drain the fat and set it aside when done.
In a large stock pot: add your onions, potatoes, garlic, chicken broth and water. Cover and bring it to a boil, and then reduce to medium heat. Cook until potatoes are done, about 30 minutes.
Add the cooked hot Italian sausage to the pot. Let boil for ten minutes. Then at the kale, simmer for another ten minutes. Make sure you don't add the stems to the soup. Personally, I don't like the texture and I find the taste is bitter. *Updated February 12, 2014: I have found the kale to still be a little too crunchy so I simmer for twenty minutes*.
Bring the simmer down to a lower heat and add your cream and red pepper flakes. Heat through, I usually let it go from another ten or so minutes.