For the Cake

1. Preheat the oven to 350°F and set an oven rack in the middle position.
2. Spray 3 or 2 (9-inch) round cake pans with nonstick cooking spray with flour, such as Baker’s Joy or Pam with Flour. Line the bottoms of the pans with parchment circles and spray again.
3. Place the chocolate in a medium heatproof bowl. Bring the water to a boil in the microwave (or on the stovetop) and pour over the chocolate; let sit for one minute. Stir until the chocolate is melted and the mixture is completely smooth.
4. In a medium bowl, using an electric mixer, beat the egg whites on high speed until stiff peaks form, 1 to 2 minutes. Set aside and clean the beaters (you’ll use them again for the batter).
5. In a medium bowl, whisk together the flour, cocoa powder, baking soda and salt. Set aside.
6. In a very large bowl, using an electric mixer, beat the butter and sugar until light and fluffy, about 3 minutes (start on low, then increase the speed to medium). Add the egg yolks, one at a time, beating well after each addition. Blend in the melted chocolate mixture and the vanilla. On low speed, add the flour mixture in three additions, alternating with the buttermilk, beginning and ending with the flour.
7. Add about ⅓ of the egg whites to the cake batter; fold until evenly combined. Add the remaining egg whites and fold just until the batter is uniform. Divide the batter evenly into the prepared pans.
8. Bake until the cakes are set and a toothpick inserted into the centers comes out clean, 25 to 30 minutes for 3 layers or 35 to 40 minutes for 2 layers. Cool the cakes in the pans for about 15 minutes, then turn out onto wire racks to cool completely.

For the Coconut-Pecan Frosting

1. In a 2-quart saucepan, whisk together the egg yolks, evaporated milk, and light brown sugar; add the butter and bring to a gentle boil. Cook over medium-low heat, whisking frequently, until thick, about 12 minutes (adjust the heat as necessary to keep the mixture at a gentle boil). Remove from the heat and stir in the coconut, pecans, vanilla, and salt. Let cool to room temperature.

For the Chocolate Glaze

1. Pour the cream and corn syrup into a medium microwave-safe bowl. Microwave on high power until boiling, about 1 minute. Add the chopped chocolate. (Alternatively, place the chocolate in a medium bowl. In a small saucepan, bring the cream and corn syrup to a boil and then pour it over the chocolate.) Let the mixture sit for 30 seconds, then whisk until smooth and glossy. Let the ganache cool until slightly thickened but still pourable, whisking occasionally so a film doesn't form on top, 10 to 15 minutes. (If it gets too thick, you can warm it in the microwave for 10 seconds, or until just pourable.)

To Assemble

1. For a 3 layer cake: Place 1 cake layer, rounded side down, on a cake platter. Using a metal spatula, spread ⅓ of the coconut-pecan frosting over the layer. Add the second layer, rounded side down; spread with ⅓ of the frosting. Add the third layer, rounded side up; spread with remaining frosting, leaving the sides of the cake unfrosted. For a 2-layer cake, follow the same procedure but spread half of the frosting over the bottom layer and the remaining half over the top layer. Prepare the chocolate glaze and drizzle it over the top of the cake, letting it drip down the sides. Cut the cake with a small, very-sharp serrated knife, using a sawing motion and wiping the knife clean (carefully!) between slices.
2. Note: If you’d like to make your own buttermilk, check out: How to Make Buttermilk.
3. Make-Ahead/Freezing Instructions: The cake can be made up to two day ahead of time and stored in a cake dome at room temperature. The cake layers can also be frozen without the frosting for up to 3 months. Let them cool completely, wrap them individually in plastic wrap, and then in foil. Thaw overnight on the countertop before assembling and frosting the cake.