-
1
Position an oven rack in the center of the oven and preheat the oven to 325u00b0F/160u00b0C/gas 3. Spray a 9-in/23-cm cake pan generously with baking spray. Line the bottom of the pan with a circle of parchment paper. Spray the parchment paper. Set aside.
-
2
Put the chopped chocolate in a medium heatproof bowl and set the bowl over a pan of barely simmering water. Warm the chocolate, stirring frequently, just until it melts. Remove the bowl from the heat, let cool for several minutes. Mash the bananas with a fork, and then stir them into the melted chocolate. Set aside.
-
3
Place the butter and brown sugar in the bowl of your KitchenAid(R) Stand Mixer fitted with the flat beater. Attach the KitchenAid(R) Sifter + Scale Attachment to your mixer. Close the ingredient valve. Weigh the flour, cocoa, baking powder, and salt in the ingredient hopper, taring the scale between ingredients.
-
4
Turn the mixer to medium-high speed, and cream the butter and sugar until light and fluffy, 2 to 3 minutes. Scrape down the sides of the bowl. With the mixer on medium speed, add the eggs, one at a time, beating well after each addition. Beat in the vanilla. Turn the mixer off and use a rubber spatula to scrape down the sides of the bowl. Add the banana mixture to the mixing bowl.
-
5
Turn the mixer to medium-low, open the ingredient valve and sift the dry ingredients into the wet ingredients in the mixing bowl. Beat just until combined. Remove the mixer bowl, and use a rubber spatula to blend in any flour remaining on the sides of the bowl. Fold in the walnuts and cocoa nibs until evenly distributed.
-
6
Spread the batter in the prepared pan. Lightly sprinkle the top with turbinado sugar and flake sea salt. Bake the cake until a toothpick inserted into the center of the cake comes out clean, 35 to 40 minutes. Let the cake cool in the pan on a wire rack. Run a table knife around the inside edge of the pan to loosen the cake. Invert the cake onto a wire rack, peel off the parchment paper, and then turn it right side up. Transfer to a cake plate and cut into wedges when ready to serve. The cake is best when served on the day it is baked. The cake will keep at room temperature for 2 days in a covered container.
