Preheat the oven to 375°F. Lightly spray 2 9-inch cake pans with baking spray. Place parchment paper in the bottom of the pan. Spray the top of the paper with baking spray. Set aside.
In a large bowl stir together the flour, baking powder, salt, and baking soda. Set aside.
In a medium-sized bowl, whisk together the sugar, brown sugar, oil, eggs, buttermilk, and vanilla until smooth. Whisk in the melted chocolate until combined.
Pour the wet mixture into the dry and whisk together until there are no lumps. Pour in the boiling water and whisk to combine.
Evenly distribute the batter between the two cake pans. Bake for 23-28 minutes until a toothpick inserted into the center comes out clean.
Let the cakes cool in the pan completely on a wire rack.
While the cakes are cooling, make the pecan coconut frosting. Place the brown sugar, sugar, butter, egg yolks, and evaporated milk.
Whisk until combined, there will be chunks of butter, that’s okay. Place over medium heat and cook, whisking constantly until it comes to a low boil. Continue to whisk until it starts to thicken, about 1 minute.
Take off the heat and add the vanilla, toasted coconut, and toasted pecans and stir it in until combined. Allow the mixture to cool to room temperature.
Once the cakes and pecan coconut frosting are cooled, make the chocolate buttercream. In the body of a stand mixer with the paddle attachment cream the butter and the melted chocolate together until smooth. Add the powdered sugar in a little at a time until fully mixed in.
Add the vanilla and 2 tablespoons of milk. Stir it in until combined. Place the mixer on to medium-high speed and whip for 3 minutes until light and fluffy. If the frosting seems too thick, add the extra 1 tablespoon of milk.
Take the cool cakes out of the pan and trim off the top if it is uneven. Place one of the cakes bottom side down onto your serving platter.
Frost with a thin layer of chocolate buttercream on top of the cake. Add half of the coconut pecan frosting on top and smooth it out almost to the edge, leaving a half-inch border.
Add the other cake, top side down on top. Add a thin layer of chocolate frosting on top and on the sides of the cake.
Add the remaining coconut pecan frosting on top of the cake, leaving a ½ inch border.
Pipe the remaining chocolate frosting around the top edge of the cake, I used a 1M star tip. Garnish with pecans halves if desired, serve immediately.