1 (8 inch) graham cracker crust
4 egg yolks
1/2 c. sugar
1/2 c. fresh key lime juice
2 c. heavy whipping cream, unwhipped
1 tbsp. confectioners' sugar
1/2 tsp. vanilla

Whisk the egg yolks with the sugar in the top of double boiler. Set over simmering heat and whisk in the lime juice. Cook, stirring often, about 10 minutes or until mixture is thick enough to coat a spoon.

Remove from heat. Cover and refrigerate until mixture is cool and thick, but not stiff. (About 1 hour.)

Whip 1 cup of cream to very stiff stage. Fold into cooled filling. Pour into prepared crust and chill.

Just before serving, whip the remaining cream with confectioners' sugar and add vanilla. Ladle cream over pie.