250g/9oz ripe banana (about 3 large bananas), mashed
275驳/9戮辞锄 plain flour
2 tsp baking powder
1 tsp bicarbonate of soda
120g/4录oz golden caster sugar
录 tsp ground cinnamon
100g/3陆oz dark or milk chocolate chips (or a mixture)
2 tbsp flavourless oil, such as sunflower or light rapeseed, plus extra for greasing
录 tsp fine salt
seeds or chopped nuts, for decorating (optional)
1 tsp vanilla extract
75g/2戮oz unsalted butter
1 large free-range egg
100ml/3陆fl oz milk