Preheat the oven to 350°F. Butter a 9”x13” pan, line with parchment paper, then lightly butter the parchment paper.
In a stand mixer or large bowl with a hand mixer, beat egg whites until stiff peaks form. Place the beaten egg whites in a separate bowl, and set aside.
In the same stand mixer bowl or large mixing bowl, cream the butter with the sugar, and melted chocolate with the electric mixer on medium speed until smooth. Add the egg yolks and vanilla and beat on medium speed until fluffy.
Add baking powder to the mixture. Gradually add the flour to the cake batter, alternating with the buttermilk, beating well after each addition and scraping the sides of the bowl as necessary. Start the mixture on low speed and gradually increase to high speed.
On low speed, add the beaten egg whites, coconut, and pecans.
Pour the batter into the prepared pan and bake 1 hour or until golden brown and fully cooked. Allow the cake to cool in the pan on a cooling rack at least 10 minutes.
Run a butter knife around the edges of the pan to loosen it from the sides. Place a flat serving cake plate or cardboard cake box base on top of the cake. Hold both the pan and base, and carefully invert them together to release. Lift off the cake pan, and slowly peel away the parchment paper.
Spread with icing.