A light, fluffy chocolate layer cake with a gentle sourdough tang and deep cocoa notes, subtly enhanced by coffee. Finished with a silky chocolate buttercream for a balanced, not-too-sweet indulgence.
In a bowl, mix together flour, coconut oil, sourdough starter, and water. Cover and allow to sit overnight or up to 24 hours (optional).
In a large bowl, mix together granulated sugar, salt, and finely ground coffee (optional).
Add eggs, vanilla, cocoa powder, and whole milk to the dry ingredients and stir to combine.
Add the sourdough mixture to the bowl and whisk until smooth.
Add baking soda and mix until incorporated.
Preheat the oven to 350ºF. Butter two 9-inch cake pans.
Divide the batter evenly between the prepared pans and bake for 30–35 minutes, or until a toothpick inserted in the center comes out clean.
Remove from the oven and cool for about 10 minutes. Turn out onto a cooling rack and let cool completely.
Make the frosting: In a stand mixer with the whisk attachment (or using a hand mixer), beat the softened butter on high speed until light and fluffy.
With the mixer on low, gradually add the cocoa powder and powdered sugar until incorporated.
Add vanilla and 3 tablespoons of heavy cream; increase speed to medium and whip until light and fluffy. Add the remaining cream if the frosting is too stiff.
Frost the cooled cake.