- 3 large eggs, separated
- ½ cup (4 ounces or 115 grams) unsalted butter, at room temperature
- 1½ cups (300 grams) granulated sugar
- 1½ teaspoons vanilla extract
- 1½ cups (375 grams) mashed bananas
- ⅔ cup (160 grams) sour cream
- 3 cups (400 grams) all-purpose flour
- ½ teaspoon ground cinnamon
- 1 teaspoon baking powder
- 1½ teaspoons baking soda
- 1½ teaspoons kosher salt
- 2 cups (12 ounces or 340 grams) semi- or bittersweet chocolate chips
- ½ cup (100 grams) granulated sugar
- 1 teaspoon ground cinnamon
Cake
Filling and topping
Make the batter: In a large bowl, beat egg whites until they hold firm peaks and set aside. [If you only have one mixer bowl, you can transfer the egg whites to another and use the mixer bowl to make the rest of the cake batter.]
In an empty mixing bowl, beat butter and 1½ cups of the granulated sugar until light and fluffy. Beat in egg yolks and vanilla. In a separate bowl, whisk flour, baking soda, baking powder, ½ teaspoon of the cinnamon, and salt together. Add banana to butter mixture and beat until combined. Add half the flour mixture, the sour cream, then the remaining flour mixture, beating each until combined. Fold in the egg whites.
Assemble the cake: Combine remaining ½ cup of the granulated sugar and 1 teaspoon cinnamon in a small bowl. Spread half of batter evenly in the prepared pan. Sprinkle with half of the cinnamon-sugar mixture and 1 cup of the chocolate chips. Dollop remaining cake batter over filling in spoonfuls. Use a rubber or offset spatula to gently spread it over the filling and smooth the top. Sprinkle batter with remaining cinnamon-sugar and remaining chocolate chips.
Bake the cake: For 35 to 40 minutes, until a tester inserted into the center of the cake comes out clean. Let cool in the pan. [Note: This takes less time in my oven than the classic version does, which is usually 40 to 50 minutes.]
To serve: Transfer cake to a cutting board and cut into squares.
Do ahead: My preference is to keep this cake at room temperature and not cover it. I will, however, press a piece of foil or plastic against the cut side. I don’t like to cover the pan or put the cake in an airtight container because it softens the flaky cinnamon-sugar topping, which feels tragic.
