For 120g mashed banana you will need one 200g very ripe banana.
60g (¼ cup) unsalted butter, softened
115g (½ cup) soft brown sugar
1 egg, at room temperature
120g (½ cup) mashed banana
100g dark chocolate, chopped
125g (1 cup) plain flour
1½ tsp ground cinnamon
1/2 tsp bicarbonate of soda
60ml (¼ cup) buttermilk
icing sugar, sifted, for dusting (optional)
1. Preheat the oven to 190C. Grease six 5cm×8cm×4cm loaf tins and line the bases with baking paper.
2. Cream the butter and brown sugar in a medium-sized bowl using electric beaters until pale and fluffy. Add the egg and beat until well combined. Stir in the banana and chocolate. In a separate bowl, sift together the flour, cinnamon and bicarbonate of soda. Fold half of the flour mixture into the chocolate mixture. Fold in the buttermilk, then add the remaining flour mixture and stir until just combined.
3. Spoon into the prepared tins and smooth the surfaces with the back of a spoon. Bake for 25–30 minutes, or until a skewer inserted in the centre of a loaf comes out clean. Allow to stand in the tins for 5 minutes, then turn out onto a wire rack to cool completely. Serve dusted with the icing sugar, if desired.
These loaves will keep, stored in an airtight container, for up to 3 days. To freeze, cover individually with plastic wrap and place in an airtight container or a freezer bag. Seal and freeze for up to 3 months. Thaw at room temperature.