Instructions

Banana Sponge Cake Layers:

1. Preheat the oven to 170ºC (conventional) and line a 20×20 cm baking pan with parchment paper.
2. In a bowl, combine all-purpose flour, baking soda, baking powder, and salt.
3. Mash the ripe bananas and set aside. Mix together the full-fat milk and vanilla extract and set aside.
4. In another bowl, whisk together granulated sugar and room temperature butter until light and airy using a strand mixer or electric hand mixer, about 2-3 minutes on high speed.
5. Add eggs one at a time on low speed until fully incorporated into the batter.
6. Gradually add ⅓ of the flour mixture, mixing well. Then add the mashed banana, followed by another ⅓ of the flour mixture. Mix in the milk and vanilla mixture. Finally, add the remaining ⅓ of the flour mixture and mix until just combined. Be cautious not to overmix.
7. Use a spatula to ensure the batter is evenly mixed. Pour the batter into the prepared baking pan and bake for 28-30 minutes, or until a cake tester comes out clean.
8. Allow the cake to cool on a rack for 5-10 minutes before gently removing it from the pan. Let it cool completely.

Chocolate Buttercream:

1. Melt the semi-sweet dark chocolate and heavy cream together either over a bain-marie or in the microwave. Let it cool to room temperature.
2. Sift the powdered sugar.
3. Cream the butter in a stand mixer or with a hand mixer on medium/high speed for about 4 minutes.
4. Add vanilla extract and the sifted powdered sugar to the butter, mixing on low speed. Scrape down the sides of the bowl and continue mixing for 2 minutes on low/medium speed.
5. Add the room temperature melted dark chocolate and mix until fully incorporated. Scrape down the sides of the bowl and mix again to ensure even distribution.
6. If the buttercream is too soft, refrigerate for 5-10 minutes before using, then mix again to achieve desired consistency.

Assembly:

1. Spread the chocolate buttercream evenly over the cooled banana sponge cake using an offset spatula.