Preheat the oven to 350°F. Generously grease two 8-inch cake pans and set aside.

In a large bowl, combine flour, sugar, cocoa powder, dark cocoa powder, baking soda, espresso powder, and salt. Mix well. Add vanilla extract, vinegar, oil, and water, stirring until the mixture is smooth and well combined.

Divide the batter evenly between the two prepared cake pans. Bake for 25-27 minutes, or until a skewer inserted into the center comes out clean.

Remove the cakes from the oven and let them cool completely. Once cooled, carefully slice each cake in half horizontally to create four thin layers.

To assemble, place the first cake layer on a flat surface and spread a generous amount of frosting over it. Add the next layer on top and repeat the process until all layers are stacked. Frost the top of the cake and refrigerate for at least 30 minutes to let it set.