¼cup(22g)cocoa powder (natural, unsweetened or Dutch-process)
¼cup(55g)boiling or VERY hot water
Coarse sugar, for sprinkling (optional)
Instructions
Preheat oven to 350 degrees F. (If using a dark-coated pan, reduce oven temperature to 325 degrees F.) Line a muffin tin with paper liners. This recipe makes about 18 muffins, so you'll need to bake a second smaller batch (or use a second muffin tin).
In a large bowl, add the bananas, granulated sugar, brown sugar, oil, sour cream, eggs, and vanilla. Whisk together until well combined.
Add the flour, baking powder, salt and baking soda. Mix until no dry streaks remain (batter will be slightly lumpy; that's ok...don't over mix).
In a medium bowl, whisk together the cocoa powder and boiling water until smooth. Add 1 1/4 cups (325 g) of the banana batter to the chocolate mixture and mix until combined and no streaks of light colored batter remain (again, try not to over mix).
Into each muffin cup: scoop about 1 1/2 tablespoons banana batter, followed by a scant 1 tablespoon of chocolate batter, followed by another 1 1/2 tablespoons of banana batter, and finishing with another teaspoon or so of chocolate batter. SEE NOTE BELOW FOR ADDITIONAL TIPS ON FILLING THE MUFFIN CUPS and what to do with extra batter.
Sprinkle a light dusting of coarse sugar over the muffin cups, if desired.
Bake for 17 to 19 minutes until the tops of the muffins spring back lightly to the touch.
Remove the muffins from the tin to a wire rack to cool completely.
Notes
Bananas:use very ripe bananas for the best flavor and mash them thoroughly so there aren't a lot of large chunks. Tips on Filling the Muffin Cups:don't overthink or stress about this part. Just keep in mind that you want to layer, not swirl, the batters. There is MORE plain banana batter than chocolate batter, so each muffin cup will have more than half plain batter with a few small scoops of chocolate batter. You'll need about 1/4 cup batter total for each muffin cup. I use a small (#80) cookie scoop for the chocolate batter and a medium (#60) cookie scoop for the plain batter (but I don't fill the cookie scoops all the way since a #80 scoop is about 1 tablespoon and a #60 scoop is about 2 tablespoons). It's ok if there is extra batter - just take a look at the muffins and add tiny scoops here and there until everything is evened out and the cups all have about the same amount of batter. I use a USA brand muffin tin. If the muffin tin you are using has slightly smaller/different size muffin cups, you may get more or less muffins out of the batch. Fill each muffin cup about 2/3 or slightly fuller with batter (if you live at high altitude, don't fill the muffin tins quite as full).