Key lime pie

To make the base, blitz the biscuits in a food processor until they are like fine crumbs and then combine with the melted butter. Press the mixture into the base and 4cm (1½") up the sides of the tin. Chill the base while you make the filling. Whisk together the filling ingredients until thick and creamy. Spoon over the biscuit base and chill for at least 1 hour. Remove the pie from the tin and place on a serving plate. Drizzle the melted chocolate over the top and leave to set. Before serving, decorate with the lime wedges and the zest.