Put the beans in a bowl, cover with water and soak for 12 hours. Peel the garlic, the onion, the carrots, clear the celery of its filaments, then chop up 1/2 stalk of celery, 1 carrot and 1/2 onion and mince the parsley. Shell prawns removing tails and the black thread, wash and dry delicately with a clean tea towel.Drain the beans, toss them into a sauce pan, add a bay leaf, the garlic, the carrot, the celery and the onion, then cover the mix with plenty of water and cook for about 70 minutes, minding that the water does not boil too soon. Once the beans are cooked, drain a small lot with a slotted spoon, keep it aside and put the rest in the vegetable mill.Pour two tbsp of oil in a saucepan and lightly fry the chopped onion, the celery and the carrot without browning them. Add the mashed beans and a scoop of warm water then blend the beans left aside and boil. Cook the pasta in plenty of salted boiling water, once drained add it to the cannellini beans cream and let it flavour for a couple of minutes.In the meanwhile brown the prawn tails in a non-stick pan with the remaining oil; once to a golden brown, add salt pepper and then drain. Pour the pasta mixed with the sauce in the dishes, then add the prawn tails and sprinkle with parsley and serve.