Cut the leeks into rings, grate the carrots on a coarse grater. Fry in olive oil. Add the bell peppers, chopped into strips, and finely chopped fennel. Fry quickly too.
Peel and dice the potatoes. Peel the Brussels sprouts from the upper leaves, divide each head of cabbage into 4 parts. For greens, this time I used radish tops, celery leaves and parsley, but you can replace them with turnip or beet tops, or spinach. A matter of taste.
Pour in the white beans cooked almost until cooked, along with the water in which they were cooked. Add water or broth. Salt. Bring to a boil. We start to cook potatoes and cabbage.
After 10 minutes add chopped greens. Cook the Brussels sprouts soup for another 5-7 minutes. If you like garlic, you can add a few minced cloves. Cover with a lid and let stand for 10 minutes.