2) For the filling, beat the egg yolks and sugar on high speed in the bowl of an electric mixer fitted with a paddle attachment for 5 minutes, until thick. With the mixer on medium speed, add the condensed milk, lime zest, and lime juice. Pour into the baked pie shell and freeze.
3) To garnish, beat the double cream on high speed in the bowl of an electric mixer fitted with the whisk attachment until soft peaks form. Add the sugar and vanilla and beat until firm. Spoon or pipe decoratively onto the pie and decorate with lime. Freeze for several hours or overnight.