Heat the oven to 350°F (175°C). Grease two 9-inch round cake pans and line the bottoms with parchment.

Whisk the flour, sugar, cocoa powder, baking powder, baking soda, and salt in a large bowl.

Add the eggs, buttermilk, oil, and vanilla. Beat for about 2 minutes, until the mixture is smooth.

Stir in the boiling water or hot brewed coffee. The batter will be thin, which is normal. Fold in the shredded coconut.

Divide the batter between the prepared pans. Bake for 30–35 minutes, until a toothpick inserted in the center comes out with a few moist crumbs.

Cool the cakes in their pans for 10 minutes, then turn them onto cooling racks. Cool completely before frosting.

For the frosting, whisk the evaporated milk, sugar, egg yolks, butter, and salt in a saucepan. Cook over medium heat, stirring constantly, for 10–12 minutes, until thick enough to coat a spoon; do not let it boil aggressively.

Remove the frosting from the heat and stir in the vanilla, coconut, and pecans. Cool it to room temperature, remembering that it thickens as it cools.

Place one cake layer on a serving plate and spread it with about one-third of the frosting. Add the second layer, then cover the top and sides with the remaining frosting.

For the optional ganache, heat the cream until steaming but not boiling. Pour it over the chopped chocolate, rest for 2 minutes, stir until smooth, cool briefly until thickened, and drizzle over the assembled cake.