To prepare a chocolate blackout wedding cake with coconut buttercream recipe, first you need to prepare your cake batter. First, you will need your chocolate cake mix. You can find it at your local grocery store, or you can buy it online. Then, preheat your oven to 350?F (180?C) and grease and flour the cake pan. Next, mix your butter and sugar together until they are light and fluffy. Add in your vanilla and chocolate extracts, and mix until combined. Finally, add in the eggs and vanilla extract. Pour the batter into the prepared pan and bake for 35 to 40 minutes or until the toothpick comes out clean. Remove the pan from the oven and let it cool for 10 to 15 minutes.