Line a loaf tin with cling film it hangs over the sides. Set aside. Blitz the berries in blender, then place a sieve over a bowl and pour the berry mixture into it, squish the berry mix through the sieve with a wooden spoon, then set aside. Discard the seeds. Put the sugar into another bowl and add 1 egg white and whisk to stiff peaks. Add the remaining egg white and keep on whisking until the mixture is very stiff, brilliant white and glossy. Put aside also. In another bowl, whip the double cream until thick, and then fold in the vanilla, whipped cream and finally the stiff egg whites. Add the prepared berry puree, but do not mix in completely to create ripples in the ice-cream. Immediately tip the mixture into the prepared loaf tin, smooth over the top and place in the freezer until firm. Ten minutes before you are ready to serve, take the tin out from the freezer, remove the cling film and allow to soften before serving.