Preheat the oven to 350 degrees F.
Whisk together condensed milk, sour cream, lime juice and lime zest. Pour the mixture into the baked pie crust, then bake for 5 to 8 minutes. The filling should not brown. in fact, it won't look like it did anything!
Remove from oven and let cool for about an hour at room temperature. Chill for at least 4 hours before serving.
At some point during the chill time, prepare the whipped cream. Whip the whipping cream until stiff peaks just start to form, then beat in the sugar and vanilla. Pipe the whipping cream decoratively around the edges.
Gingersnap Crust: Mix together all ingredients. Press into a very well greased pie dish and freeze for 10 minutes. From freezer, bake 10 minute at 350. Let cool before filling and baking again.