Adapted from Martha Stewart’s Cupcakes
3 ripe bananas
2 cups cake flour (not self-rising), sifted
1/2 tsp baking soda
1/2 tsp baking powder
1/2 tsp salt
1/2 cup (1 stick) butter
3/4 cup sugar
3 large eggs, separated
1/2 cup sour cream
1 tsp pure vanilla extract
3/4 cup chopped walnuts (optional)
Preheat the oven to 400°F. Place 3 whole unpeeled bananas on a baking sheet and roast for 15 minutes (the peels will darken). Set aside and let cool. Peel when cool.
Sift together the cake flour, baking soda, baking powder and salt.
Reduce the oven to 350°F and line muffin tins with paper liners (if you want).
With an electric mixer on medium-high, cream the butter and sugar until pale and fluffy. Add egg yolks one at a time, beating until each is incorporated, scraping down sides of bowl as needed. Add the peeled roasted bananas and beat to combine. Add flour mixture in three batches, alternating with two additions of sour cream, and beating until just combined after each. Beat in vanilla and fold in walnuts (optional).
In another bowl, with an electric mixture on medium speed, whisk egg whites to soft peaks; fold in one-third of whites into the batter to lighten. Gently fold in remaining whites in two batches.
Divide batter evenly among lined cups, filling each 3/4 full. Bake about 20 minutes or until a cake tester comes out clean. Transfer to wire racks to cool completely.