Start by prepping your cake pans well for nonstick (I use two methods for this- parchment paper cut to size and grease or spray over it) and preheat your oven to 325.
Sift or whisk together the flour, baking soda and salt. Set this bowl aside.
Next, we will melt together the unsweetened chocolate with the water. You can do this in a microwave (stopping to stir every 30 seconds until melted) or over a low heat on the stove (stirring continuously).
In a mixing bowl, cream together the sugar alternative the butter. Set the mixer on low and add the egg yolks, one at a time, mixing between additions. Then add the vanilla extract to the bowl. Next we will add the cooled melted chocolate mixture and the flour mixture adding half of each at a time, alternating additions, and mixing between additions. (ie. ½ chocolate, mix, ½ flour, mix, repeat). Then you can add the buttermilk and mix gently.
For the next step, we will need clean mixer beaters and a new mixing bowl. Using a hand mixer is one way to get around having to find an additional bowl to fit your stand mixer. This is where we will beat the egg whites until they form stiff peaks. Then, folks these stiff peaked egg whites into the bowl with the cake batter.
Bake this cake for 28-30 minutes or until a toothpick comes out clean.