Mix together the biscuit crumbs, half the sugar and the melted butter and press over the bottom and up the sides of a greased 23 cm (9 inch) springform tin. Refrigerate while making the filling.
Beat the egg yolks lightly together until creamy. Add the condensed milk, lime and lemon juice and lime rind and beat until well mixed and slightly thickened. In another bowl, beat the egg whites until stiff. Add the remainder of the sugar and continue beating until the meringue holds soft peaks (see
Spoon the filling into the crumb crust and smooth the top. Bake in a preheated oven, 160°C (325°F), Gas Mark 3, for 15–20 minutes or until the filling is just firm and lightly browned on top. When cool, refrigerate the pie for at least 3 hours, until it is well chilled.
Whip the cream until it begins to thicken. Add the icing sugar and vanilla extract and continue whipping until it forms thick swirls. Spread the cream over the top of the chilled pie. Decorate with twisted lime slices, if liked. Remove the side of the pan just before serving and serve well chilled.