Preheat oven to 350 degrees F (180 degrees C) and place oven racks in the upper and lower third of the oven. Lightly butter and flour, and line the bottoms of three - 8 x 2 inch deep round baking pans with parchment paper.
Sift the flour, cocoa powder, baking powder, baking soda, and salt into a medium bowl.
Melt the chopped chocolate and coffee, or water, in a glass bowl over a pot of simmering water. Make sure the water doesn't touch the bowl.
In the bowl of your stand mixer, or with a hand mixer, beat the butter until smooth and creamy. Add 1 3/4 cups of sugar (reserving the rest for the egg whites) and continue beating until the mixture is fluffy (this will take about three to five minutes). Scrape down the sides of the bowl as needed. Add the eggs yolks, one at a time, mixing well after each addition.
Add the vanilla extract and beat to combine. Then add the melted chocolate and beat until incorporated.
Add the flour mixture and butter milk in three additions, beginning and ending with the flour mixture. Beat only until the ingredients are mixed together.
Beat the egg whites in a separate bowl at high speed. Slowly drizzle in the 1/4 cup of reserved sugar as mix. Once soft, almost stiff peaks form, mix about a cup of the egg whites into the batter to lighten it then carefully fold the remaining the egg whites into the batter.
Divide the batter evenly among the three prepared pans and smooth the tops. Bake for about 30 - 35 minutes or until a toothpick inserted in the center comes out clean and the tops spring back when lightly pressed. Rotate the pans about halfway through baking to ensure even baking. Remove from oven and place on a wire rack to cool for about 15 minutes. Butter or lightly spray with a non stick vegetable spray a wire rack before inverting the cakes onto the rack to prevent the cakes from sticking. Cool the cakes completely before frosting.