1. Preheat your oven to 350°F (175°C). Grease and line three 8-inch round cake pans with parchment paper.

2. In a large bowl, whisk together flour, granulated sugar, brown sugar, cocoa powder, baking powder, baking soda, and salt.

3. In a separate bowl, combine buttermilk, eggs, vegetable oil, and vanilla extract. Add the wet mixture to the dry ingredients and mix until just combined.

4. Slowly stir in the boiling water. The batter will be thin.

5. Divide the batter evenly between pans. Bake for 25–30 minutes or until a toothpick comes out clean. Let cool for 10 minutes in the pans, then transfer to wire racks to cool completely.

6. To make the filling: In a saucepan, whisk together evaporated milk, egg yolks, sugar, and butter. Cook over medium heat, stirring constantly, until thickened (about 10–12 minutes). Remove from heat and stir in vanilla, coconut, and pecans. Let cool.

7. For the ganache: Heat the cream until just simmering. Pour over chocolate and let sit for 2–3 minutes. Stir until smooth. Let cool slightly to thicken.

8. Assemble the cake: Place one cake layer on a plate. Spread with half of the filling. Repeat with second layer and remaining filling. Top with third layer and pour ganache over the top.

9. Garnish with toasted coconut or pecans if desired. Chill for 30 minutes before slicing.