60gramsDutch-process cocoa powder, ½ cup (I used Varlhona)
100gramschocolate chips / chunks, ½ cup
Preheat oven to 175C / 350F (non fan-assisted). Melt butter in a small pot over low heat. Remove melted butter from heat then take some of the butter and grease a round baking tin (7-inch diameter x 2-inch tall) or a 1-litre loaf tin (8x4-inch x 2.5-inch tall). Line the bottom of the tin with parchment paper. Set aside.
Peel the bananas and place them in a large mixing bowl. Mash the bananas with a fork or potato masher. It's okay if there are still small chunks left.
Pour in the melted butter and whisk with a wire whisk until incorporated. Whisk in the brown sugar, then egg and vanilla.
Sift in flour, cocoa powder, baking soda and salt. Use a large spoon and fold in the dry ingredients in a figure-of-eight motion until just incorporated - stop when you don't see any more streaks of flour. Use a rubber spatula and scrape the bottom of the mixing bowl to ensure all the dry ingredients are mixed in. Do not overmix.
Add in the chocolate chips/chunks and stir gently to mix together.
Scrape the batter into the tin. Bake for 50 to 60 minutes, until any skewer inserted into the center of the cake come out clean with only melted chocolate stains.
Remove the tin from the oven and set over a wire rack. Cool for 15 minutes then run a thin spatula along the edges of then tin. Turn the cake out, and peel off the parchment paper. Turn it right side up onto a wire rack and let cool.
Serve then cake warm or at room temperature. Store cake in an airtight container, or wrapped with foil in the refrigerator.