For The Cake For The Topping

For The Main

1. Preheat oven to 325°F (300°F convection). Grease and line an 8x4-inch loaf pan with parchment paper (let it extend 2 inches above the top of the pan). In a large bowl, whisk together the sugar, flour, baking soda, cocoa powder, and chopped chocolate.
2. In a separate bowl, mash the bananas. Stir in the whole egg plus 2 egg yolks, oil, and milk. In a clean bowl, whip the egg whites until stiff peaks form. Quickly whisk the wet banana mixture into the dry ingredients, then whisk in a quarter of the egg whites to lighten the batter. Gently fold in the remaining egg whites.
3. Pour the batter into the prepared pan and bake for 1 hour 10-15 minutes, or until a toothpick inserted into the center comes out clean. Let cool in the pan on a wire rack.

1. To make the icing, melt the chocolate and sour cream together in a heatproof bowl set over a pan of barely simmering water. Refrigerate until spreadable. Remove the cake from the pan and spread the icing on top. Sprinkle with the banana chips.