In a large bowl add 1 1/2 cup of sugar, 4 egg yolks, 16 tbsp of butter (at room temperature), 2 tsp vanilla extract, and buttermilk. Mix until the ingredients are nice and creamy.
In a separate bowl, add the cake flour, salt, baking soda, and baking powder. Soft or stir the ingredients together, until well incorporated.
Gradually add the dry ingredients in with the wet, while using a handheld mixer to mix in the ingredients. Once the cake batter is nice and creamy, set the bowl to the side.
Place 2 oz of semi sweet chocolate, and 2 oz of unsweetened chocolate into a bowl, then pour 1/3 cup of hot coffee over the chocolate. Let it stand for a couple minutes, then mix until everything is nice and creamy, and let it cool down until it's luke warm.
Once the chocolate cools down, add it into the cake batter, and mix it in thoroughly.
Next, grab the bowl of egg whites, and use a handheld mixer to beat/mix them until they are nice and fluffy.
Add the fluffy egg whites to the cake batter, and fold it in until everything in the batter is well combined
You will need two 9' cake pans. Spray each pan with baking spray, then pour the cake batter into the pan. Each pan should be full up to 1 inch of the pan.
Bake the cakes on 350 F, for 25-30 minutes each.
Remove from the oven, and place the cake on a cooling rack