Peel the prawns. Prepare the fish broth by frying half a carrot, half an onion and half a rib of celery; add the prawn shells, add half a glass of white wine and leave to evaporate. Then add cold water, bring to the boil and then lower the flame and continue to cook very slowly for 1 hour. In another pan prepare the vegetable broth with the remaining vegetables. Cut into the upper part of the prawns and remove the black thread and cut into small rounds. In a pan brown the prawns in a drizzle of oil on a high heat, add salt and pepper to taste, then add the brandy and let it all evaporate. Add the rice and begin to roast, adding the rest of the white wine. Continue adding half the fish broth and half the vegetable broth and finish cooking. Clean the melon well, removing all the peel and pips, cut into pieces and add to the rice at the end of the cooking. Stir in the butter and cheese. Dust with some more salt and pepper and serve.