Spray 3 (8-inch) cake pans with baking spray and line with parchment paper circles.
Combine ½ cup boiling water and espresso powder in a heat-proof container.
Place the chocolate in a heat-safe bowl and pour in the hot espresso water. Whisk the chocolate until smooth and set aside to cool.
In a medium bowl, combine the cake flour, baking soda, and salt.
In a stand mixer or with a hand mixer, cream together the sugar, butter, and vegetable oil until pale and fluffy.
Beat in the egg yolks one at a time.
Add the vanilla and cooled chocolate and mix until fully incorporated.
Add ⅓ of the flour mixture to the bowl and mix just until moistened.
Use a rubber spatula to scrape down the sides of the bowl and mix in half of the buttermilk. Continue to alternate the flour mixture with the buttermilk, mixing and scraping after each addition, and finishing with the flour.
In a separate mixing bowl, beat the egg whites until stiff with clean beaters.
Carefully fold ⅓ of the whites into the batter to lighten it.
Fold in the remaining whites until the batter is uniform in color.
Divide the cake batter between the 3 pans.
Bake the layers for 25-30 minutes, or until a tester inserted in the center comes out clean.
Remove the cakes from the oven and cool completely in the pans on a wire rack.
While the cake layers are baking, line a baking sheet with parchment paper and add the chopped pecans and coconut in an even layer.
Bake for 5 minutes, until the nuts are slightly toasted and the coconut just starts to turn golden.
Remove the pan from the oven and immediately transfer the pecans and coconut to a large bowl.
In a heavy saucepan, combine the evaporated milk, brown sugar, butter, yolks, and salt.
Cook over medium-low heat, stirring constantly, until the mixture thickens enough to coat the back of a spoon.
Pour the custard over the coconut and pecans. Add the vanilla and stir to combine. Set the filling aside to cool.
To make the ganache, place the chocolate in a medium heat-proof bowl.
Bring the cream and butter just to a boil in a small saucepan.
Pour the hot cream over the chocolate and let sit for 5 minutes.
Whisk the ganache until smooth and set aside.
To assemble the cake, invert the layers from the pans using a rack or a plate set over the top of the pans.
Place one layer on a round cake board or plate.
Add about ⅓ of the filling and spread in an even layer.
Top with another layer, followed by ⅓ of the filling, then finish with the last layer on top, bottom-side-up.
Spread the remaining filling in an even layer over the top.
Once the ganache has cooled to a good spreading consistency, ice the sides of the cake.
Garnish the cake with pecan halves, if desired.
Chill the cake for at least 4 hours to set up, then slice and serve.