Warm some olive oil in a cast iron pot, and set a large pan of water on to boil for the pasta.
Chop 1 onion and add it to the olive oil, along with a some salt and red chili flakes. While the onion softens, mince 2 cloves of garlic and prepare a package of sausage by removing the casings and roughly chopping the sausages. Remove and discard the stems from 2-3 stalks of lacinato kale and cut the leaves into fine ribbons.
Add the garlic, sausage and kale to the onion, and cook, stirring frequently, until the meat is evenly browned.