How to Make It
Preheat oven to 325°F. Place egg whites in a large bowl and beat to break up. Add coconut and mix until evenly moistened. Transfer to a 9-inch pie plate and, using a flat-sided measuring cup, press the coconut firmly into the bottom and up the sides of the plate (it will kind of mound around the edge—that’s OK).
Bake coconut crust until golden brown around the edge and light golden in the center, 40 to 45 minutes. Let cool.
Meanwhile, make the caramel. Combine sugar, water, and corn syrup in a medium saucepan over medium heat. Cook, undisturbed until beginning to turn golden brown around the edge, about 5 minutes. Continue to cook, swirling pan occasionally until mixture is evenly amber in color. Remove from heat and, using a wooden spoon (not metal!) stir in butter, cream, and salt until melted and smooth. Let cool slightly then poor into cooled crust.
Make the chocolate layer. Place chocolate in a large bowl. Heat the coconut milk and a pinch flaky salt in a small saucepan until just simmering; pour over chocolate and let sit a few minutes. Starting in the center, stir mixture until chocolate melts and mixture is smooth and evenly combined; pour over caramel layer and smooth top. Sprinkle with flaky salt and toasted coconut and refrigerate until firm, 2 hours and up to overnight.
Bring to room temperature before slicing and serving.