Preheat the oven to 325 degrees F. Grease and flour three 9-inch pans lined with parchment paper.
Heat the water and chocolate together in a microwave for about 1 minute. Stir the mixture. Place in the microwave again if needed to melt the chocolate. Allow the chocolate to cool before adding it to the other ingredients.
Cream the butter and sugar in the bowl of a stand mixer on medium speed for 5 minutes, or until light and fluffy.
Add the eggs one at a time, beating well after each addition.
Scrape the sides and bottom of the bowl very well.
Add the chocolate mixture and combine.
Combine the cake flour, baking soda, and salt in a bowl and mix with a wire whisk.
Combine the buttermilk and vanilla in a liquid measuring cup.
Alternately add the flour mixture and the buttermilk mixture, beginning and ending with the flour mixture, beating until well blended.
Scrape the sides and bottom of the bowl and incorporate any unmixed batter if necessary.
Beat the batter for 3 minutes on medium speed.
Divide the batter evenly between the three prepared pans. Tap the pans on the counter to ensure there are no air bubbles.
Bake for 30 minutes. Test doneness by touching a cake top. If it springs back, it is done. If the indentation stays, it needs 2 to 3 minutes longer.
Cool the cakes for at least 10 minutes on a cooling rack before removing from the pans.
Place the coconut and pecans in a bowl together and set aside.
In a medium saucepan, melt the butter over medium heat.
Add the evaporated milk and sugar and bring to a boil.
Slowly add half of the milk mixture to the egg yolks, whisking vigorously until combined.
Place the egg mixture back in the saucepan and stir constantly over medium heat for about 3 to 4 minutes, until you see a bubble and the mixture has thickened.
Pour the egg and milk mixture over the pecans and coconut.
Add the vanilla and stir until well blended.
Let the icing cool.
Once the icing is cool, spread it between the cake layers, sides, and on top.