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1. Preheat your oven to 175°C (350°F). Grease and line two 20 cm (8-inch) round cake tins with parchment paper.
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2. In a large bowl, mash the very ripe bananas thoroughly with a fork until completely smooth — no large lumps. The riper the bananas, the sweeter and more intensely flavored your sponge will be.
3 piece Very ripe bananas
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3. In a separate bowl, whisk together the flour, cocoa powder, baking soda, baking powder, and salt until evenly combined. Set aside.
2 cup All-purpose flour,
0.5 cup Unsweetened cocoa powder,
1.5 tsp Baking soda,
1 tsp Baking powder,
0.5 tsp Salt
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4. In a large mixing bowl, beat the softened butter with the granulated sugar and brown sugar using an electric mixer on medium-high speed for 3–4 minutes until light and fluffy. Add the eggs one at a time, beating well after each addition, then mix in the vanilla extract and the mashed bananas.
3 piece Very ripe bananas,
0.5 cup Unsalted butter, softened,
1 cup Granulated sugar,
0.5 cup Light brown sugar,
2 piece Eggs,
2 tsp Vanilla extract
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5. Reduce mixer speed to low. Alternate adding the dry flour mixture and the sour cream into the butter mixture, beginning and ending with the dry ingredients (three dry additions, two wet). Mix until just combined — do not overmix. Finally, stir in the hot coffee by hand with a spatula; the batter will be loose and glossy. The coffee deepens the chocolate flavor dramatically.
0.5 cup Sour cream,
0.5 cup Hot coffee (or hot water)
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6. Divide the batter evenly between the two prepared tins. Bake for 30–35 minutes, or until a skewer inserted into the center comes out clean. Let the cakes cool in the tins for 10 minutes, then turn out onto a wire rack and allow to cool completely before frosting — at least 1 hour.
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7. Make the ganache base: place the finely chopped dark chocolate in a heatproof bowl. Heat the heavy cream in a small saucepan over medium heat until it just begins to simmer (do not boil). Pour the hot cream over the chocolate and let it sit undisturbed for 2 minutes, then stir from the center outwards until silky smooth. Let the ganache cool to room temperature, about 20–30 minutes.
200 g Dark chocolate (70%), finely chopped,
1 cup Heavy cream
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8. Once the ganache is at room temperature and slightly thickened, beat in the room-temperature butter cubes using an electric mixer until completely incorporated and fluffy. Sift in the powdered sugar and cocoa powder and beat on medium speed for 2–3 minutes until the frosting is thick, glossy, and spreadable. If it is too soft, refrigerate for 10 minutes and beat again.
0.5 cup Unsalted butter, cubed and room temperature,
2 cup Powdered sugar,
0.2 cup Unsweetened cocoa powder (for frosting)
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9. Place one cooled cake layer on a serving plate or cake stand. Spread a generous layer of chocolate frosting evenly over the top. Place the second cake layer on top, pressing gently to adhere.
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10. Apply a thin crumb coat of frosting all over the top and sides of the cake using an offset spatula. Refrigerate for 15 minutes to set the crumb coat, then apply the remaining frosting generously over the entire cake, smoothing the sides and swirling the top for a finished look. Refrigerate for at least 20 minutes before slicing and serving.
