Preheat oven to 350°. Lightly grease 3 (9-inch) round cake pans, line bottoms with parchment paper, and lightly grease paper.
Microwave chocolate and 1/2 cup water in a large bowl at HIGH 1 to 1 1/2 minutes or until chocolate is melted, stirring halfway through heating time. Set aside.
Combine flour, baking soda, and salt in a medium bowl; set aside.
Beat egg whites at high speed in the bowl of an electric mixer fitted with whisk attachment until stiff peaks form. Transfer to another bowl.
Fit mixer with paddle attachment; beat butter and sugar at medium speed until light and fluffy. Add egg yolks, 1 at a time, beating well after each addition. Stir in reserved chocolate mixture and vanilla. Add reserved flour mixture alternately with buttermilk, beating until smooth after each addition. Gently fold in egg whites.
Pour batter into prepared pans. Bake at 350° for 25 to 30 minutes or until cake springs back when lightly touched in center. Remove from oven, and run a spatula between cakes and sides of pans. Let cool 15 minutes, remove cakes from pans, and remove parchment paper. Let cool completely on wire racks, and freeze layers 1 hour. Spread Coconut-Pecan Frosting between layers and over top and sides of cake.
*For testing purposes, we used Baker's German's Sweet Chocolate