Preheat and Prepare
Preheat your oven to 350°F (175°C). Grease and flour three 9-inch round cake pans, then line the bottoms with parchment paper. This helps the cakes release easily.
Melt the Chocolate
In a heatproof bowl, combine the boiling water and German chocolate. Stir until smooth, then let it cool to room temperature.
Mix the Dry Ingredients
In a medium bowl, whisk together the flour, baking soda, baking powder, and salt.
Cream the Butter and Sugar
In a large bowl, beat the butter and sugar until light and fluffy (about 3 minutes). Add the eggs, one at a time, mixing after each addition. Stir in the vanilla extract.
Combine Wet and Dry
Add the melted chocolate mixture to the batter. Alternate adding the dry ingredients and buttermilk, beginning and ending with the flour mixture. Mix until smooth and glossy.
Bake
Divide the cake batter evenly among the pans. Bake for 25–30 minutes or until a toothpick inserted in the center comes out clean. Let the cakes cool in the pans for 10 minutes, then transfer to a rack to cool completely.
Make the Coconut Pecan Frosting
In a saucepan over medium heat, whisk together evaporated milk, sugar, egg yolks, and butter. Cook, stirring constantly, until thickened (about 10–12 minutes).
Remove from heat and stir in vanilla, coconut, and pecans. Allow it to cool completely before spreading.
Assemble the Cake
Place one cake layer on a serving plate. Spread one-third of the frosting evenly over the top. Repeat with the next layer and finish with the remaining frosting on top.
You can leave the sides unfrosted for a rustic look or spread a thin layer for a fully covered cake.