Preheat oven to 350 and prepare two 9 inch cake pans with butter and parchment rounds. Set aside.

In a large mixing bowl, combine the sifted flour, cocoa powder, espresso powder, salt, butter, and neutral oil. Mix until the flour is paste-like and smooth, then mix in the baking powder and baking soda.

Separately, in a medium size mixing bowl, combine the sour cream, sugar, eggs, and vanilla. Whisk until smooth, then add the mashed banana. Mix, then transfer into the butter and flour mixture. Fold in the wet ingredients until just combined, then add in the chopped chocolate and fold once more.

Evenly divide the batter between the cake pans, smoothing out the surface into a flat layer. Tap the pans on the counter a few times to release air bubbles, then place on the center rack of the oven. Bake for 25-35 minutes, or until the cake begins to pull away from the edges, and a cake tester comes out clean when inserted in the middle.

Remove from the oven and allow to cool for 15 minutes or so, before transferring out of the pan onto a cooling rack to cool completely. To make the assembling easier, I freeze my cake rounds, so they don't tear when I spread the frosting. So I recommend transferring to the freezer while you make the frosting. You can also store in the freezer overnight and assemble the cake the next day.

Insert or link to FROSTING RECIPE directions

For a firmer, spreadable frosting, refrigerate for about 30 minutes before frosting the cake.

To assemble, remove cake from the freezer and place on a stand or wide, flat plate. Add about half of the frosting to the center and spread just to the edges. Place the top layer on and continue frosting the top—put a large dollop in the center and use a mini offset spatula to push out and down the sides. I’m not much of a baker, so a rustic look is perfect if you don’t want to cover the sides completely.