In a large saucepan melt the butter then add the onion and cook over a medium gentle heat for about 5 minutes or until they are translucent. Add the Carnaroli (risotto) rice and lightly toast in the saucepan, stirring constantly for two minutes. Pour in the white wine and zest of one lemon; continue to cook over a medium heat until the wine is completely absorbed. Add the first ladle of Simon Gault Home Cuisine fish stock and allow to simmer, stirring occasionally until the stock is almost completely absorbed. Repeat until the last of the stock has been added, this will take roughly 20-25 minutes. Once you have only 250mls of Simon Gault Home Cuisine fish stock left add the prawn cutlets. If the risotto is too thick then add a little more stock to make it ooze onto the plate. Season to taste with salt and pepper, stir in the parmesan cheese and curly leaf parsley, then serve.