Crumble sausage in a large soup pot or dutch oven, cast iron if you have it, and cook over medium heat until no longer pink. Stir in onion, garlic and chili pepper and cook until translucent taking care not to let them brown. Depending on your sausage, you may need to add a bit of extra virgin olive oil.
Add the kale and chicken stock- it will cook down rapidly so don't panic if it overwhelms your pot at first. Just give it a few minutes.
When the kale has cooked down a bit, add the tomatoes, potato, bay leaves, thyme and saffron. Let the soup simmer for about 30 minutes or until the potato is tender and the kale is cooked to the consistency you like.
Ladle into soup bowls and enjoy with crusty bread.