Chocolate Banana Apple Oat Cake

Chocolate Banana Apple Oat Cake

This square oat cake combines banana, grated apple, cocoa, and ground rolled oats for a moist, close crumb. A thin dark-chocolate yogurt topping and chopped walnuts echo the fruit-and-nut interior without relying on a diet-program claim. Measuring the banana and squeezing excess apple juice prevent a wet band through the center.

Equipment, yield, and timing

• Equipment: blender or food processor, box grater, two bowls, 8-inch square metal pan, parchment, whisk, spatula, rack, and instant-read thermometer
• Yield: 9 squares
• Preparation: 20 minutes
• Bake: 28 to 35 minutes at 350°F
• Cool: at least 1 hour before topping

Ingredients

Cake:

• 1 1/2 cups old-fashioned rolled oats, 135 grams
• 1/3 cup natural unsweetened cocoa powder
• 1 1/2 teaspoons baking powder
• 1/2 teaspoon ground cinnamon
• 1/4 teaspoon fine salt
• 1 cup mashed ripe banana, about 2 medium
• 1 cup peeled grated apple, lightly squeezed
• 2 large eggs
• 1/2 cup plain Greek yogurt
• 1/4 cup maple syrup
• 2 tablespoons neutral oil
• 1 teaspoon vanilla extract
• 1/3 cup chopped walnuts, divided

Topping:

• 2 ounces semisweet chocolate, finely chopped
• 1/4 cup plain Greek yogurt, room temperature

Method

1. Heat the oven to 350°F. Line the pan with parchment. Grind the oats to a fine flour, then whisk with cocoa, baking powder, cinnamon, and salt.
2. Whisk banana, apple, eggs, 1/2 cup yogurt, maple syrup, oil, and vanilla. Fold in the oat mixture and half the walnuts just until uniform.
3. Spread in the pan and bake 28 to 35 minutes. The center should spring back, a tester should show moist crumbs without wet batter, and the center should reach about 200°F.
4. Cool 15 minutes in the pan, then lift onto a rack and cool completely.
5. Melt chocolate in 15-second microwave intervals, stirring each time. Cool 3 minutes, then fold in the room-temperature yogurt gradually. Spread over the cake, add remaining walnuts, chill 20 minutes, and cut nine squares.

Cues and troubleshooting

Large bananas or very juicy apples cause a gummy center, so measure both after preparation. Squeeze the grated apple firmly once; it should remain moist but should not drip. If the topping seizes, the chocolate was too hot or the yogurt too cold; warm it gently in 5-second intervals while stirring. Coarse oats make fragile edges, so grind until no intact flakes remain and the meal feels fine between two fingers. Do not top a warm cake because trapped steam loosens the chocolate layer.

Substitutions and storage

Pecans can replace walnuts, or omit nuts for a nut-free cake after checking chocolate labels. Honey can replace maple syrup. Refrigerate the topped cake within 2 hours and keep covered at 40°F or below for up to 4 days. Let portions stand 10 minutes before serving. Freeze the untopped cake for up to 2 months; thaw wrapped in the refrigerator before adding the topping.