Preheat the oven to 180°C (160°C fan-forced).
Grease and line one or two loaf tins (1 - 36 cm x 10cm, or 2 – 18 cm x 10 cm).
Melt butter in a small saucepan and set aside until ready to use.
In a large bowl, mix together the yoghurt and bicarbonate of soda. Leave to stand for 5 minutes.
In another large bowl, sift the flour, baking powder and cinnamon. Add the oats.
Stir the melted butter, raw sugar and eggs into the yoghurt mixture.
Fold the yoghurt mixture into the flour mixture, then gently stir in the mashed bananas.
Pour into the loaf tin or tins and sprinkle the blueberries and rolled oats over the top.
Bake in the oven for 1 to 1 1/4 hours until a skewer inserted into the centre of the loaves comes out clean.
Set aside to cool for about 30 minutes, then turn onto a wire rack to cool completely.
Store in an airtight container in a cool place for up to three days. The banana bread is delicious heated up the next day and slathered with butter or ricotta. It’s suitable to freeze.