Preheat the oven to 350°F (175°C).,In a bowl, combine the crushed Chin Chin crumbs and sugar. Add the melted butter and mix until the crumbs are evenly coated.,Press the Chin Chin mixture into the bottom of a 9-inch pie pan, forming an even crust. Bake for 10 minutes, then remove from the oven and set aside to cool.,For the lime filling, in a medium bowl, whisk together the sweetened condensed milk, lime juice, lime zest, egg yolks, and vanilla extract until smooth and well combined.,Pour the lime filling into the cooled Chin Chin crust and spread it out evenly.,Bake the pie for 15-18 minutes, or until the filling is set but still slightly wobbly in the center.,Let the pie cool to room temperature, then refrigerate for at least 3 hours, or overnight, to allow the filling to firm up.,Before serving, top with whipped cream, if desired, and garnish with lime slices or zest.