1. If you prefer to long-ferment this cake, read the directions in the Notes first! You will prepare parts of the batter the night before.
2. Preheat the oven to 350 degrees F and line two 9-inch cake pans with butter and parchment paper. Set to the side

DRY INGREDIENTS

1. In a medium mixing bowl, sift together the flour, natural cocoa powder, baking soda, espresso powder and salt. Add the sugars, then whisk until combined. Make sure there are no clumps of brown sugar. Set to the side. 

   Note: Cocoa powder is notorious for having clumps, so be sure to not skip the sifting! This recipe calls for unsweetened natural cocoa powder, not Dutch-processed cocoa powder. The acidity of the natural cocoa powder reacts with the baking soda to help this cake rise. 
   220 grams all-purpose flour, 75 grams unsweetened, natural cocoa powder (not Dutch-processed), 12 grams baking soda, 2 grams espresso powder, optional, 6 grams salt, 200 grams sugar, 220 grams light brown sugar

WET INGREDIENTS

1. In a separate bowl, whisk together the room-temperature sour cream, eggs, neutral oil, vanilla extract and sourdough discard until smooth. 

   You can use active sourdough starter, as well. Just be sure to use the same amount in grams.
   180 grams sour cream, room temperature, 2 eggs, 115 grams neutral oil, like avocado oil, 8 grams vanilla extract, 120 grams sourdough discard

COMBINE

1. Pour the wet ingredients into the dry ingredients, then mix with a rubber spatula until there are no more streaks of flour. The batter will look very thick, like brownie batter. 
2. Pour in the hot water and whisk until combined. This will thin out the cake batter.

   You want the water to be hot, about 110 degrees F. This helps “bloom” the cocoa powder which will enhance the cocoa flavor. 
   180 grams hot water
3. Divide the cake batter evenly into the prepared cake pans. Gently drop the cake pans on the countertop to remove any air bubbles from the batter.

BAKE

1. Bake the Sourdough Chocolate Cake for 20-25 minutes. The cake is done when a toothpick comes out mostly clean with a few moist bites of cake. 
2. Remove the cake from the oven and place on a wire rack to cool completely. 

   Note: It is normal for a chocolate cake to slightly sink in the middle even when it’s been completely baked through. Cocoa powder isn’t as strong as all-purpose flour. There is a lot of moisture in this moist chocolate cake.

CHOCOLATE BUTTERCREAM  FROSTING

1. In a stand mixer with a whisk attachment, beat the room-temperature butter on medium speed for 2 minutes, or until light and fluffy.

   This can also be done with a hand mixer.
   226 grams unsalted butter, softened
2. Next, add the powdered sugar, one cup at a time at medium speed.
   400 grams powdered sugar
3. Finally, add the cocoa powder, heavy cream, vanilla and a pinch of salt. Beat of medium high for 2 minutes or until light and fluffy.
   50 grams unsweetened cocoa powder, 45 grams heavy cream, pinch of salt, 8 grams vanilla extract
4. Directions on how to assemble and decorate below.