In a bowl, beat 1 cup of the whipping cream with a mixer to soft peaks.

In another bowl, combine the sweetened condensed milk, lime zest, and lime juice.

Fold the condensed milk mixture into the whipped cream. Spoon mixture into the prepared pie crust. Cover and freeze for 2 to 4 hours or until firm.

To serve, whip remaining 1 cup of whipping cream along with the powdered sugar and vanilla with a mixer to firm peaks. Spread over pie. Cut into slices and top with a lime slice if desired. Serves 8.