For the Cake Layers:

Preheat oven to 350°F. Grease and flour three 9-inch round cake pans. Line bottoms with parchment paper.

Place chocolate in small bowl and pour boiling water over it. Stir until completely melted and smooth. Set aside to cool.

In a large bowl, cream together butter and sugar until light and fluffy, about 3-4 minutes.

Beat in egg yolks one at a time, then stir in vanilla and melted chocolate mixture.

In a separate bowl, whisk together flour, baking soda, and salt.

Gradually add dry ingredients to chocolate mixture, alternating with buttermilk (beginning and ending with flour). Mix just until combined.

In a clean bowl with clean beaters, whip egg whites until stiff peaks form.

Gently fold whipped egg whites into batter until no white streaks remain.

Divide batter evenly among three prepared pans. Bake for 25-30 minutes, until a toothpick inserted in center comes out with a few moist crumbs.

Allow cakes to cool in pans for 10 minutes, then remove to wire racks to cool completely.

For the Coconut-Pecan Frosting:

Spread pecans on baking sheet and toast in 350°F oven for 8-10 minutes until fragrant.

In a medium saucepan, combine evaporated milk, sugar, egg yolks, and butter. Cook over medium heat, stirring constantly, until thickened (about 10-12 minutes).

Remove from heat and stir in vanilla, coconut, and toasted pecans. Allow to cool until thick enough to spread, about 30-45 minutes.

Assembly:

Place one cake layer on serving plate. Spread approximately one-third of frosting on top (not on sides).

Top with second layer and repeat with another third of frosting.

Place final layer on top and spread with remaining frosting, leaving sides unfrosted.