Prep: Preheat oven to 350°F (175°C). Grease and line three 8-inch pans. Separate eggs and chop chocolate.
Melt Chocolate: Stir chopped chocolate with boiling water until smooth. Cool.
Dry Mix: Whisk flour, baking soda, and salt together.
Cream Butter & Sugar: Beat butter and sugar until fluffy. Add egg yolks, vanilla, and melted chocolate.
Combine: Alternate adding flour mix and buttermilk to the chocolate batter, starting and ending with flour. Mix gently.
Whip Egg Whites: Beat egg whites to stiff peaks. Fold into batter carefully.
Bake: Divide batter into pans. Bake 25–30 minutes. Cool completely on racks.
Make Frosting: Cook evaporated milk, sugar, egg yolks, and butter until thick. Stir in vanilla, coconut, and pecans. Cool.
Assemble: Layer cakes with frosting between each. Frost the top. Optional: garnish with toasted coconut or chocolate.