Whisk together sweetened condensed milk, egg yolks, passion fruit, and sour cream. Pour into the crust and bake for 10 minutes.
Chill in the refrigerator for at least 4-6 hours, or overnight.
When ready to serve, whip heavy cream and powdered sugar until soft peaks form. Pipe or spread on the pie. Top with coconut flakes or fresh lime zest if desired.