Melt the butter in a bowl in the microwave. Place the biscuits into a food processor and blend into fine crumbs. Add the melted butter and blend again. Line the base of an 18 cm spring form cake tin with greaseproof paper and spread the biscuit mixture evenly out across the base. Press the mix down well so that it becomes firm and compact. Soak the gelatine leaves in a bowl of cold water for 10 minutes. Toss the berries into a pan and heat slowly until they start to simmer. Simmer the berries until they start to fall apart easily. Grate the lime peel finely and toss the grated peel into a bowl together with the juice from ½ a lime. Sieve the cooked raspberries into the bowl with the lime to remove the seeds. Squeeze the water out of the softened gelatine leaves and place them in a bowl with the warm raspberry purée. Stir so that the gelatine leaves dissolve. Pour the egg whites into a bowl and add the Hermesetas Granulated. Beat the mix until it becomes light and airy. Stir the mascarpone into the egg mixture and add the puréed raspberries. Continue to stir until the mixture reaches a fine, uniform consistency. In a separate bowl, whip the cream until it is light and airy. Fold the whipped cream gently into the mascarpone. Line the insides of the spring form cake tin with a plastic cake liner and pour the cheesecake over the biscuit base. Place the cake in the fridge for a minimum of five hours or, ideally, overnight. Decorate the cake with fresh raspberries immediately before serving.