Make cake according to directions and allow to cool.
For the coconut frosting: Combine egg yolks, sugar, milk, butter and vanilla in a large saucepan over medium heat. Stir constantly until it has began to thicken, about 12 minutes. Add in coconut and pecans and stir until thick enough to spread. Remove from heat and allow to cool slightly.
For the chocolate buttercream: Place the butter in a large bowl and beat with an electric mixer. Slowly add the powdered sugar, cocoa powder, melted chocolate, vanilla and salt. Add heavy cream as needed to thin.
Frost the center of the cake with the coconut frosting and the sides with the chocolate buttercream frosting. Enjoy with a cold glass of milk!