Prep Cake Pans: Grease and line with parchment paper.
Mix Dry Ingredients: Whisk flour, sugar, cocoa, baking soda, baking powder, and salt.
Mix Wet Ingredients: Combine buttermilk, oil, eggs, and vanilla.
Combine Wet and Dry: Mix until smooth, then stir in hot water carefully.
Bake Cakes: Divide batter evenly and bake 30–35 minutes. Check doneness with toothpick.
Cool Cakes: Let cool in pans 10 minutes, then transfer to wire rack.
Prepare Frosting: Cook sugar, evaporated milk, butter, and egg yolks until thickened.
Add Coconut and Pecans: Stir in coconut, pecans, and vanilla; cool slightly.
Frost Cake: Place one cake layer on a serving plate, spread frosting on top, add second layer, then frost top and sides.