• Preheat the oven to 180°C (356°F) and grease and line two 8-inch round cake pans.
• In a large bowl, mix together the flour, cocoa powder, salt, baking powder, and baking soda. Set it aside.
• In a separate bowl, whisk together the sourdough starter, eggs, vanilla, oil, milk, and sugars.
• Pour the wet mixture into the flour mixture and fold gently for a minute before pouring over the hot coffee.
• Mix briskly together but don't over mix.
• Pour into the prepared cake pans and bake for 25-30 minutes until a skewer inserted into the cakes comes out clean.

Chocolate Buttercream

• In a bowl of a stand mixer fitted with a whisk, beat the butter until light and creamy.
• Carefully add in half the powdered sugar and cocoa powder and beat on low speed until combined. The cocoa powder will puff up so take care! Add in the remaining powdered sugar.
• Once incorporated, beat on high for 5 minutes and add in 2-3 tablespoons of milk or cream as needed until it is light, creamy, and spreadable.

Chocolate Ganache

• In a small saucepan, heat the cream until just simmering. Take it off the heat and add the chopped chocolate.
• Leave it to sit for 5 minutes, then stir until it is glossy and all the chocolate has melted.
• Let it cool down until it has thickened a bit before pouring on the cake.