Peel the prawns and use it’s shells to make a stock, sauté the shells with the celery, red onion, 3 cloves garlic in butter until browned, add 2 ltrs water, bring to the boil and simmer for 45 min. Blend the stock with the shells in and strain well, add the tomato pulp in and simmer. Chop the prawns, leek and garlic, saute in butter and olive oil until lightly browned than add the rice and stir continuously. pour in the wine and stock gradually than simmer on low heat until rice is cooked through. Slice the courgette, chop the basil and mix with the risotto, add also half the chevre crushed and the walnuts. Stir well the rice and serve topped with a slice of the chevre left and some rocket leaves.