Heat the oil in a large saucepan over a medium heat, then add the onion and garlic and cook until softened. Add the sausages and cook until golden brown,
Add the tomatoes and vegetable stock and season to taste with the salt and pepper.
Finally, add the cavolo nero or savoy cabbage and simmer slowly, uncovered, over a verl low heat for 2 hours.
To serve, spoon into bowls and finish with a spoonful of creme fraiche and a sprinkling of parsley.