The night before you want to bake your cake, ferment the base of your batter. In a bowl, combine with a whisk the flour, cocoa powder, sourdough discard, white sugar, sour cream, buttermilk or milk, and ½ cup of avocado oil (reserve ¼ cup for later). Cover the bowl with plastic wrap, and refrigerate overnight.

The next day, remove bowl of batter from refrigerator and allow to rest on the counter for roughly 4 hours.

In a medium mixing bowl, add your eggs and egg yolks. Add the remaining ¼ cup of avocado oil and your melted butter (slightly cooled). Add vanilla. Whisk this mixture together until pale and smooth. Set aside.

Next, brew the amount of coffee you need or mix your hot water and espresso powder together. Set this aside.

To the bowl of your base batter, add the egg/oil/butter mixture. Whisk until smooth or use hand mixers ON LOW to incorporate the batter. Sprinkle baking powder, baking soda, and salt into the batter. Mix until just combined.

Lastly, pour the hot coffee or espresso into the batter and mix until just combined.

Preheat oven to 350°F (175°C). Grease and lightly flour two 9-inch pans or one 9x13 baking pan. If using 2 9-inch cake pans, divide batter evenly between the two pans. Set your timer for 40 minutes. Check cake at 40 minutes, inserting a toothpick to check doneness.

When cakes are done cool slightly in pans, then turn out onto racks. Allow to cool completely.

In a microwave safe bowl, melt chocolate chips. Heat at 30 second intervals, stirring between. Allow to cool.

In a stand mixer or a large bowl, add your butter. Cream on high for 3-4 minutes until pale and fluffy. Sift in cocoa powder, and add salt and espresso powder to frosting if using. Whip on medium high until frosting is smooth.

Add cooled melted chocolate to the frosting. Whip on high until frosting is glossy and smooth.

Add sifted powdered sugar to icing. Beat sugar into icing. Add vanilla and half of the cream to the icing. Whip on high until frosting starts to become light and fluffy.

For a two-tier cake: If frosting a two-tier cake, remove cakes from the freezer, and place 1 cake upside down on cake stand. Use half of the chocolate icing to frost the 1st layer of cake. When first layer of cake is smoothly covered in icing, place second layer upside down on top of the first.

For a single sheet cake: turn cake upside down onto serving platter. Spread frosting over the top and sides of the entire cake, smoothing with a spatula. Slice cake and serve!