2ouncesbittersweet or semisweet chocolate, chopped
2ouncesunsweetened chocolate, chopped
16tablespoonsunsalted butter, at room temperature, (2 sticks)
1 1/2cupssugar, divided
4large eggs, separated
1cupbuttermilk, at room temperature
For the filling:
3large egg yolks
6tablespoonsbutter, cut into small pieces
1cuppecans, toasted and finely chopped
1 1/3cupsunsweetened coconut, toasted
For the syrup:
For the chocolate icing:
8ouncesbittersweet or semisweet chocolate, chopped
2tablespoonslight corn syrup
To make the cake:
Preheat the oven to 350 degrees F. Grease the edges of two 9-inch round cake pans. Dust with flour and tap out the excess. Line the bottom of each pan with a circle of parchment paper.
Melt the chopped chocolate with the water in a heatproof bowl set over a pot of simmering water. Stir until smooth, then set aside until it cools to room temperature.
In the bowl of an electric mixer fitted with the paddle attachment, beat the butter and 1 1/4 cup of the sugar until light and fluffy, about 5 minutes. Beat in the melted chocolate. Add the egg yolks, one at a time.
In a medium bowl, stir together the flour, baking powder, baking soda and salt. Mix in half of the dry ingredients into the creamed butter mixture beating on low speed until incorporated. Mix in the buttermilk and the vanilla until combined. Mix in the remaining dry ingredients.
In a clean dry bowl of an electric mixer fitted with the whisk attachment, beat the egg whites until the form soft, droopy peaks. Slowly add the remaining 1/4 cup of sugar and continue beating until stiff peaks form. Using a rubber spatula, fold about one-third of the egg whites into the cake batter to lighten it. Then fold in the remaining egg whites just until incorporated.
Divide the batter between the prepared cake pans and bake for 45 minutes, until a toothpick inserted into the center comes out clean. Allow to cool in the pans for 10 minutes, then remove from pans and transfer to a wire rack to cool completely.
To make the filling:
While the cakes are cooling, in a medium saucepan combine the cream, sugar, and egg yolks. Put the butter, salt, toasted coconut and pecan pieces in a large bowl; set aside. Heat the cream mixture and cook, stirring constantly until the mixture begins to thicken and coat the back of the spoon (about 170-175 degrees F on an instant read thermometer). Pour the hot custard into the pecan-coconut mixture and stir until the butter is melted. Cool completely to room temperature. It will thicken as it cools.
To make the syrup:
In a small saucepan, heat the sugar and water until the sugar has dissolved, stirring occasionally. Remove from heat and stir in the dark rum.
To make the icing:
Place the chopped chocolate in a bowl with the corn syrup and butter. Heat the cream in a small saucepan over medium heat until it just begins to boil. Remove from heat and pour over the chocolate. Let stand one minute, then stir until smooth. Chill thoroughly in the refrigerator until firm enough for icing the cake.
To assemble the cake:
Using a serrated bread knife cut both cake layers in half horizontally. Set the first layer on a cake plate. Brush well with syrup then spread 3/4 cup of the coconut filling over the cake layer. Set another cake layer on top. Repeat, brushing each layer with the syrup and then spreading 3/4 cup of the coconut filling over each layer, including the top. Ice the sides of the cake with the chocolate icing and pipe a decorative border around the top.