Chocolate Banana Fudge Cake
A deeply fudgy chocolate banana cake baked in a square pan and finished with a glossy 5-minute fudge frosting. One bowl, no mixer, and naturally sweetened with ripe bananas.
Equipment
- 8×8-inch square baking pan
- Large mixing bowl
- Small saucepan
- Rubber spatula
- Whisk
- Wire cooling rack
Ingredients
WET INGREDIENTS
- 1/2 cup 115g unsalted butter, melted and slightly cooled
- 1 cup 200g granulated sugar
- 1/2 cup 100g packed light brown sugar
- 2 large eggs room temperature
- 1 tsp pure vanilla extract
- 1 1/4 cups approx. 3 medium bananas smooth mashed ripe bananas
- 1/3 cup 80ml buttermilk
DRY INGREDIENTS
- 1 1/2 cups 190g all-purpose flour
- 1/2 cup 50g Dutch-process unsweetened cocoa powder
- 1 tsp baking soda
- 1/2 tsp baking powder
- 1/2 tsp fine sea salt
MIX-INS
- 3/4 cup 130g semi-sweet chocolate chips
FUDGE FROSTING
- 1/2 cup 115g unsalted butter
- 1/3 cup 35g Dutch-process cocoa powder
- 1/4 cup 60ml whole milk
- 2 cups 240g powdered sugar, sifted
- 1 tsp pure vanilla extract
- Pinch of fleur de sel optional
Instructions
- Preheat oven to 350°F (175°C). Grease an 8×8-inch square pan and line with parchment paper, leaving an overhang on two sides.
- Whisk flour, cocoa powder, baking soda, baking powder, and salt in a large bowl until fully combined.
- Whisk melted butter, granulated sugar, and brown sugar in a second bowl. Add eggs one at a time, whisking after each. Stir in vanilla, mashed bananas, and buttermilk.
- Pour wet ingredients over dry ingredients. Fold gently with a spatula until just combined and no white streaks remain. Fold in 1/2 cup chocolate chips. Do not overmix.
- Pour batter into prepared pan and smooth the surface. Scatter remaining 1/4 cup chocolate chips on top. Bake for 32–35 minutes, until the edges are set and a toothpick inserted in the center comes out with moist crumbs, not wet batter. Cool in the pan for 15 minutes.
- Make the frosting: In a small saucepan over medium-low heat, whisk together butter, cocoa powder, and milk until the butter is melted and the mixture is smooth and steaming. Do not boil. Remove from heat. Stir in sifted powdered sugar and vanilla until glossy and smooth.
- Pour warm frosting over the slightly cooled cake. Spread gently to the edges. Scatter fleur de sel if using. Let set for 30 minutes at room temperature before slicing into squares with a warm, dry knife.
Notes
Note 1 — Storage: Store covered at room temperature up to 4 days, or in an
airtight container in the fridge up to 6 days. Freeze individual slices up to
3 months — wrap in plastic wrap, place in a freezer bag. Thaw at room temp
1 hour before serving. Note 2 — Substitutions: Replace butter with neutral oil or melted coconut oil
for a dairy-free version. Use oat milk + 1/2 tsp apple cider vinegar in place
of buttermilk. Dutch-process cocoa can be replaced with natural cocoa — the
color will be lighter and the flavor slightly sharper. Note 3 — Texture tip: Do not overbake. The toothpick should come out with
moist crumbs, not clean. The cake finishes setting as it cools, and the fudgy
crumb firms up further overnight.
airtight container in the fridge up to 6 days. Freeze individual slices up to
3 months — wrap in plastic wrap, place in a freezer bag. Thaw at room temp
1 hour before serving. Note 2 — Substitutions: Replace butter with neutral oil or melted coconut oil
for a dairy-free version. Use oat milk + 1/2 tsp apple cider vinegar in place
of buttermilk. Dutch-process cocoa can be replaced with natural cocoa — the
color will be lighter and the flavor slightly sharper. Note 3 — Texture tip: Do not overbake. The toothpick should come out with
moist crumbs, not clean. The cake finishes setting as it cools, and the fudgy
crumb firms up further overnight.