Ingredients
Equipment
Method
- Choose very ripe bananas. Use bananas with lots of brown spots, soft flesh, and a strong banana smell. They should mash very easily.
- Preheat the oven. Preheat to 350°F / 175°C. Position a rack in the center.
- Prepare the pan. Grease a 9 x 13 x 2-inch / 23 x 33 x 5-cm metal pan. Line with parchment if desired.
- Make the crumb topping. In a medium bowl, mix the crumb flour, sugar, and cinnamon.
- Add the crumb oil and vanilla. Pour in the oil and vanilla. Stir with a fork, then use your fingertips to squeeze some of the mixture into small clumps.
- Check the crumbs. You want loose sandy crumbs, pea-sized pieces, and a few larger clusters. If the mixture looks too wet, add flour 1 Tbsp at a time.
- Add the chocolate chips. Fold in all 7 oz / about 200 g chocolate chips. Set aside.
- Mash the bananas. Mash the bananas in a large bowl until mostly smooth. A few tiny pieces are fine. You should have about 2 cups / 450-500 g.
- Add the sugar. Whisk in the 2 cups / 400 g sugar.
- Add the eggs. Whisk in the 2 eggs until evenly combined.
- Add the oil. Whisk in the 3/4 cup / 180 mL oil.
- Add the mayonnaise. Whisk in the 1/2 cup / 120 g mayonnaise until no white streaks remain.
- Add soy milk and vanilla. Mix in the soy milk and vanilla.
- Combine the dry ingredients. In a separate bowl, whisk the flour, baking soda, and salt for about 30 seconds.
- Add dry to wet. Add the flour mixture to the banana mixture. Fold or mix on low only until the last dry streak disappears.
- Check the batter. It should be thick, creamy, very moist-looking, and easy to spread.
- Fill the pan. Spread the batter evenly into the prepared pan.
- Add the chocolate crumb. Scatter the crumb topping evenly over the whole surface. Do not press it firmly into the batter.
- Bake. Bake at 350°F / 175°C for about 50-60 minutes. Begin checking around 45-50 minutes.
- Check for doneness. Insert a toothpick into a cake area, avoiding a chocolate chip or obvious banana pocket. A few moist crumbs are fine, but there should be no wet batter.
- Protect the top if needed. If the topping is browned before the middle is done, cover loosely with foil and continue baking in 5-minute increments.
- Optional thermometer check. About 200-205°F / 93-96°C in the center is a useful secondary check.
- Cool completely. Place the pan on a wire rack and cool for about 1 hour before slicing.
Notes
Make Ahead, Storage & Freezing
- Make ahead: Excellent made 1 day ahead; the banana flavor becomes more noticeable after resting.
- Room temperature: Store tightly covered for 2-3 days.
- Refrigerator: Up to 5 days. Let refrigerated pieces come closer to room temperature before serving.
- Freezer: Wrap cooled pieces tightly and freeze for up to 2 months.
