Adjust the oven rack to the middle position. Preheat oven to 350°F. Grease 2- 9 inch round cake pans, line with parchment paper, and then grease and flour the parchment paper and sides of the pans. Set aside.
In a small bowl combine the flour, baking soda, and salt. Set aside.
In a second small bowl combine the cocoa powder and chopped chocolate. Add the boiling water to the bowl, cover the bowl and let sit for 5 minutes. After 5 minutes, whisk the chocolate mixture until smooth. Let the chocolate mixture cool to room temperature.
Using a stand mixer fitted with a paddle attachment cream the butter, granulated sugar, and brown sugar on medium speed until light and fluffy, about 3 minutes. Add eggs one at a time, beating well after each addition.
Add the vanilla and beat on medium high speed until light and fluffy, about 1 minute. Scrape down the sides of the bowl.
Add the chocolate mixture, and beat again (about 30-45 seconds). Scraping down the sides of the bowl so that everything is evenly combined.
With the mixer on low alternate adding the flour mixture and sour cream, starting and ending with the flour. (Flour, sour cream, flour, sour cream, flour).
Divide the batter evenly amongst the two pans.
Bake for 30 minutes or until a toothpick inserted in the center comes out clean.
Remove cake pans from the oven and place on a wire rack for 10 minutes.
Remove the cakes from the pans (discard the parchment) and let cool completely on wire rack.
Remove the coconut frosting from the fridge and stir in the pecans.
Once cake is cool, slice the two cakes horizontally to create 4 layers.
Place a cake layer on a cake stand, add 1 cup of the frosting to the top of the cake layer and spread to the edge of the cake. Add another cake layer to the top of the frosting, and continue adding 1 cup of the frosting until you’ve used all of the cake layers and the frosting is gone. Keep the sides of the cake bare. *