Put the biscuits in a blender or food processor, and whiz briefly to make crumbs.
Use some of the melted butter to grease a 900g/2lb loaf tin. Line the tin with cling film, then brush the cling film with the rest of the butter. Spoon about 3 tablespoons of the biscuit crumbs into the loaf tin, and put in the freezer for at least an hour.
Put the eggs, icing sugar and ginger in a bowl, and whisk together for 5–10 minutes until the mixture is thick and mousse-like.
Whisk the cream until soft peaks form, then fold into the egg mixture. Put 3 tablespoons of the biscuit crumbs to one side, then fold in the remainder. Pour the mixture into the prepared loaf tin, and sprinkle with the reserved biscuit crumbs.
Cover with cling film and freeze for at least 3 hours. Serve cut into 1cm/1⁄2in slices.