This Ding Dong cake has two soft, moist chocolate cake layers, a light and creamy vanilla filling, and a rich dark chocolate ganache poured over the top.
Prep: Preheat your oven to 180°C (350°F) and line two 8-inch cake pans with parchment paper.
Dry Ingredients: In a large mixing bowl, add the flour, sugar, salt, baking powder, and baking soda, sift in the cocoa powder, and whisk together.
Wet Ingredients: Add the buttermilk, vegetable oil, vanilla extract, and eggs, and mix until almost combined.
Coffee: Add the hot coffee and mix just until no lumps of flour remain. The batter will be thin and smooth.
Bake: Divide the batter evenly between the pans, weighing it for even layers and using cake strips if you have them. Bake for 25 to 30 minutes, until a toothpick comes out clean.
Cool: Let the layers cool completely before assembling.
Make the cream filling
Cook the Base: In a saucepan, whisk the flour and sugar together, then add the milk. Cook over medium heat, whisking constantly, until it simmers. After 2 minutes, it will thicken into a pudding. Remove from the heat.
Cool the Base: Pour it into a shallow dish, press plastic wrap onto the surface, and chill for at least 1 hour, or 30 minutes in the freezer, until completely cool.
Whip the Butter: Whip the softened butter and vanilla extract with an electric hand mixer for 2 to 3 minutes, until smooth and fluffy.
Combine: Add the cooled base a spoonful at a time and whip on high speed for 3 to 5 minutes, until the filling looks like whipped cream.
Make the chocolate ganache
Heat: Place the chopped dark chocolate and heavy cream in a bowl and microwave for about 1 minute.
Stir: Let it sit for 10 minutes so the chocolate melts, then stir until smooth and glossy.
Assemble the cake
Anchor: Pipe a small dollop of filling onto your cake board and place the first cake layer on top.
Fill: Spread the cream filling evenly over the first layer with a spatula.
Stack: Top with the second cake layer and smooth out the filling around the sides. Chill for 10 to 15 minutes.
Ganache: Pour the ganache over the top and spread it with an offset spatula so the entire cake is coated. Chill for at least 30 minutes before slicing.
Notes
Baking Soda: ⅔ teaspoon is about ½ teaspoon plus a heaping ⅛ teaspoon.
Thin Batter: The batter is very thin because of the coffee. That is normal.
Even Layers: Weigh the batter and use cake strips for flat layers.
Cool the Filling Base: It must be completely cool before whipping it into the butter, or the filling will be runny.
Add It Slowly: Add the base a spoonful at a time so the filling doesn't curdle.
Ganache Consistency: It should be pourable but not runny. Cool it longer if it slides off the cake.
Chill Before Slicing: The cake slices best cold.
Evaporated Milk: Works in place of heavy cream in the ganache.
Make Ahead: Bake the layers the night before and keep them wrapped in the fridge.
Storage: Keep covered in the fridge for up to 4 days. Freeze the whole cake or slices for up to 2 months.