I hope everyone knows the secret about baking with bananas: You need to use very, very, very ripe bananas—almost black on the outside. And the best way to be sure you have them when you want them is to frequently let some get ripe on the counter and then peel them and put the gooshy innards in a zipper bag in the freezer—labeled, of course, because, trust me, they will become completely unrecognizable. Then when you get a hankering for banana bread or cake, you can just defrost them and proceed with the recipe! This coffee cake is really, really good.
Nut-Crusted Chocolate-Banana Swirl Cake
For the Pan:
softened unsalted butter
2 Tbsp sugar
1/3 cup (1 1/4 oz.) medium-fine chopped walnuts
For the Cake:
2 cups all-purpose flour
2 tsp baking powder
1/4 tsp baking soda
1/4 teaspoon salt
3/4 cup unsalted butter, at room temperature
1 1/4 cups sugar
3 medium very ripe bananas, peeled
2 tsp vanilla
3 large eggs
6 Tbsp buttermilk
4 oz. bittersweet chocolate, melted and cooled slightly
Prepare the pan: Position a rack in the middle of the oven and heat the oven to 350°. In a small bowl, mix the sugar with the chopped walnuts. (I just put the whole walnuts, which I’d weighed out, in my little chopper thingy with the sugar and pulsed ‘em.) Generously butter a large bundt pan and coat with the nuts and sugar, pressing the nuts with your fingers to help them stick. The pan sides will be coated and some of the nuts will fall to the bottom; that's fine.
Make the cake: In a medium bowl, whisk the flour, baking powder, soda, and salt until well blended. In an electric mixer on medium-high speed, beat the butter, sugar, bananas, and vanilla until well blended and bananas are almost smooth. Add eggs one at a time, beating just until incorporated. Remove the bowl from the mixer. Add half of the flour mixture and stir gently with a rubber spatula just until blended. Add the buttermilk and stir just until blended, and then add the rest of the flour and stir just until blended. Spoon half the batter into a medium bowl and gently stir in the melted chocolate just until combined.
With a large spoon, alternately add a scoopful of each batter to the pan, working around the pan until all the batter is used. Gently run a knife through the batter, once clockwise and once counterclockwise, to swirl the batters slightly. Gently tap the pan on the counter to settle the ingredients.
Bake until a toothpick inserted in the center comes out with just a few crumbs on it, about 40 minutes. (Mine took closer to 45 minutes.) Transfer the pan to a rack to cool for 15 minutes. If you wait too long, the cake will stick to the pan, and if you unmold it too early, it can break into chunks. Run a thin knife around the pan sides, being careful not to dislodge the nuts, to loosen the cake. Invert the pan onto the rack, lift off the pan, and let the cake cool completely.