Preheat oven to 350 F. Grease 8x8 baking dish and line with parchment paper and set aside.
Crush Nilla Wafers and graham crackers in food processor or Ziploc bag with a rolling pin, until fine. In a medium mixing bowl, mix crumbs, brown sugar, and melted butter until crumbs are well coated. Press crumbs evenly into bottom of the pan. Bake for 7 minutes or until golden. Set aside to cool completely, at least 30 minutes.
In a large mixing bowl, whisk together sweetened condensed milk, sour cream, and lime juice until well combined, using a rubber spatula to scrape edges and ensure all is combined.
Pour filling evenly on top of cooled crust, bake for 10-15 minutes, it will still be somewhat jiggly but it will become firm once chilled. Set aside and let cool for about 30 min-1 hour, transfer to the refrigerator for at least 3 hours.
To make the whipped cream, whip heavy cream until soft peaks form. Add sugar and vanilla extract then whip until semi-stiff peaks form. Pipe or spread onto bars. Dip a sharp knife in hot water before cutting to make clean cuts.