Preheat the oven to 180°C/160°C fan/350°F/gas mark 4. Grease a 2lb loaf tin (approx 11.5 x 21.5 cm / 4.5 x 8.5 in) and line it with baking parchment.
Mash the banana really well in a large bowl. Whisk in the sugar, melted butter or oil, milk, vinegar and vanilla extract.
330 g (peeled weight) very ripe banana, 175 g (1 cup) light brown soft sugar, 120 g (½ cup) vegan block butter, melted, 60 g (¼ cup) unsweetened non-dairy milk (I use soy), ½ teaspoon cider or white wine vinegar, 1 teaspoon vanilla extract
Whisk in the baking powder, bicarbonate of soda, cinnamon, nutmeg and salt.
1 teaspoon baking powder, ½ teaspoon bicarbonate of soda (baking soda), 1 teaspoon ground cinnamon, ¼ teaspoon ground nutmeg, ¼ teaspoon table salt
Add the flour and stir with a balloon whisk until no dry lumps remain but be careful not to over-beat the batter. Fold in the chocolate chips.
250 g (2 cups) plain (all-purpose) flour, 125 g (¾ cup) chocolate chips
Pour the batter into the prepared tin and spread it level. Bake for 50-60 minutes until firm and springy to the touch and a skewer inserted into the centre (avoiding any chocolate chips) comes out clean.
Leave to cool in the tin for 20 minutes then carefully turn out onto a wire rack and leave to cool completely. Once cold, store in an airtight container for up to five days.