Make the crust: Preheat the oven to 325 degrees F. In a food processor (or high powered blender), pulse the pecans, crackers, coconut, and sugar, until the mixture is fully ground. You want very fine crumbs that are all the same size. Transfer the crumbs to a large bowl, stir in the butter, and stir well with a rubber spatula until evenly combined. Pour crumbs into a 9- or 10-inch pie plate, spreading them with your fingers into an even layer. Use the flat bottom of a measuring cup or drinking glass to press and pack the crumbs evenly into the bottom of the pie plate, then use the side of the measuring cup to press crumbs into the plate’s sides. Bake until fragrant and golden browned, 12 to 15 minutes. Let cool on a wire rack while you make the filling.
Make the filling: In a large saucepan, whisk the sugar, cornstarch, and salt together. Whisk in the coconut milk and whole milk until fully mixed, taking care to scrape all sides and corners of the saucepan (so as not to leave any clumps of cornstarch). Set the saucepan over medium heat and cook, whisking constantly, until the mixture is thickened and simmering across the entire surface, about 10 minutes. Remove the pan from heat. Whisk in the chopped semisweet and unsweetened chocolate and butter until melted and fully blended. Whisk in the vanilla. Pour the filling into the cooled pie crust. Press a sheet of plastic wrap over the surface of the filling (it should be laying against the filling, touching it) and let the pie cool for 1 hour. Refrigerate until the filling is firmly set, at least 6 hours or up to 24 hours.
Make the topping: In a stand mixer fitted with whisk attachment, whip the cream, sugar, and vanilla on medium speed until foamy, about 1 minute. Increase the speed to high and whip until stiff peaks form, about 2 minutes. Smooth the whipped cream evenly over your chilled pie, sprinkle with chocolate shavings, and serve.