Sauté the chopped onion in a crock pan with olive oil, chilli to taste and a drizzle of water; add the tomato and the celery leaves and simmer for about ten minutes. Add the previously boiled beans and let cook for 5/6 minutes with salt.
Clean the mussels and put them in a frying pan over high heat until the mussels open. Remove some of the clams from shells and add them to the pan with the cooking water of the mussels.
Cook the Maltagliati in salted boiling water for about 2 minutes, drain the egg pasta by holding the water and let it cook in the pan with the sauce adding water as needed. Serve garnished with mussels with shells kept warm and enjoy!