1Make the chocolate simple syrup by heating together ½ cup of water and ½ cup of granulated sugar until the sugar is fully dissolved, then mix in 1 tablespoon of dark cocoa powder.
2Whisk together the dry ingredients: 2 cups of all-purpose flour, 2 cups of granulated sugar, ¾ cup of dark cocoa powder, 2 teaspoons of baking powder, 1 ½ teaspoons of baking soda, and 1 teaspoon of fine salt.
3Combine the wet ingredients: 1 cup of warm water, 1 cup of sour cream, ½ cup of vegetable oil, 2 large eggs, 2 teaspoons of vanilla extract, and 1 teaspoon of instant espresso.
4Pour the wet ingredients into the dry ingredients and whisk together until smooth.
5Pour the batter into lined and greased 8-inch cake pans (3 layers) and bake at 350°F for 22-26 minutes.
6While the cakes are baking, prepare the chocolate frosting by mixing together 2 cups of unsalted butter, 1 cup of dark baking cocoa, 1 teaspoon of vanilla extract, and ½ teaspoon of salt.
7Mix in 5 cups of powdered sugar and ¾ cup of heavy cream.
8Mix in 1 ⅓ cups of melted and cooled dark chocolate.
9Brush cake layers with chocolate simple syrup and spread an even layer of chocolate frosting between each layer.
10Add one thick layer of chocolate buttercream frosting to the top of the cake.
11Decorate the edges of the cake with extra cake crumbs (optional).