Squeeze the sausage meat from the cases into a bowl. Add the fennel seeds and squeeze to mix together then shape into 16 small balls.
Heat 2 tbsp oil in a large pan over a medium high heat and brown the meatballs all over then set aside.
In a large saucepan heat 1 tbsp oil and gently fry the onion, leek and celery for 5 minutes. Add garlic and celeriac and fry for a few minutes more then add 800ml of the stock. Simmer for 15 minutes then add the cavolo nero, orzo and meatballs and remaining stock to the soup. Simmer for a further 10 minutes.
Heat 1 tbsp oil in a frying pan with the butter and fry the breadcrumb gently for 5-10 minutes until golden. Spread on a plate to cool then mix with the parmesan.
Add the cannellini beans to the soup and cook for a minute or two more than serve with a scattering of the cheesy crumbs.
Notes
Packed with seasonal vegetables and sausage meatballs spiked with fennel seeds, it embodies the essence of hearty comfort food.