1 1/2 cups sugar, plus more for unmolding the cake
8 tablespoons unsalted butter, softened at room temperature
1/3 cup unsweetened Dutch-process cocoa powder
1 teaspoon baking soda
1/4 teaspoon baking powder
1/3 cup melted unsweetened Bakers chocolate
1/2 cup hot water
4 extra-large eggs, at room temperature
1/2 cup buttermik
Unsalted butter, for greasing two cake pans
Position a rack in the center of the oven, and preheat the oven to 350F.
Put the flour, sugar, butter, cocoa, baking soda and baking powder in the bowl of a stand mixer fitted with the paddle attachment. (If you dont have a stand mixer, you can put the ingredients in a bowl and use a hand mixer with the blending attachments.) Mix on slow just until the ingredients are blended together, a few seconds, then raise the speed to low-medium and continue to mix until smooth, approximately 1 additional minute.
Stop the motor and pour in chocolate. Mix for 1 minute, then, with the motor running, pour in the hot water. Then add the eggs, 1 egg at a time, adding the next one after the previous one has been absorbed into the mixture. Stop the motor periodically and scrape the bowl from the bottom with a rubber spatula to integrate ingredients, and return the mixer to low-medium speed. After all the eggs are added, continue to mix for an additional minute to ensure the eggs have been thoroughly mixed in. This will help guarantee that the sugar is dissolved and that the flour has been thoroughly mixed in, which will help produce a luxurious mouth-feel in the final cake.
With the motor running, add the buttermilk, stopping the motor to scrape the sides and bottom. Continue to mix for another minute or until the mixture appears smooth. Before baking, be sure the batter is at 70-73F or the cake will crown.
Grease two 9-inch cake pans (2 inches high) with the butter, and flour them.
Divide the batter evenly between the two cake pans, using a rubber spatula to scrape down the bowl and get as much batter as possible out. Bake until the cake begins to pull from the sides of the pan and is springy to the touch, 25 to 30 minutes.
Remove the cakes from the oven and let cool for at least 30 minutes, preferably an hour. The cakes should be at room temperature before you remove them from the pan. Put a piece of parchment paper on a cookie sheet, top with sugar, and one at a time, turn the pans over and turn the cakes out onto parchment; the sugar will keep it from sticking. Refrigerate or freeze until ready to decorate.