In a large bowl, combine 1 1/2 cups of sugar, 4 egg yolks, 16 tablespoons of butter (at room temperature), 2 teaspoons of vanilla extract, and buttermilk. Mix until ingredients are creamy. 2 tsp vanilla extract, 1 1/2 cups granulated sugar, 4 large eggs at room temperature, 16 tbsp of unsalted butter, 1 cup buttermilk
In a separate bowl, add the cake flour, salt, baking soda, and baking powder. Sift or stir the ingredients together until well incorporated. 2 cups 4 tbsp of cake flour, 1 tsp baking powder, 1 tsp baking soda
Gradually add the dry ingredients to the wet ingredients, using a handheld mixer to mix together. Set the bowl aside.
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 stand for a couple of minutes, then mix until creamy, and let cool until lukewarm. 2 oz semi sweet chocolate, 2 oz unsweetened chocolate, 1/3 cup black coffee
Once the chocolate cools down, add it to the cake batter and mix thoroughly.
Use a handheld mixer to beat egg whites until fluffy.
4 large eggs at room temperature
Add egg whites to the cake batter, and fold until batter is well combined.
Spray two 9" cake pans with baking spray. Pour the cake batter into the pans. Each pan should be full up to 1 inch of the pan.
Bake the cakes at 350°F for 25-30 minutes.
Remove from the oven and place the cake on a cooling rack