2 ripe bananas (175g/6oz peeled weight), roughly mashed
2 level tsp baking powder
3 tbsp light muscovado sugar
50ml/2fl oz rapeseed oil, plus a little extra for greasing
125²µ/4½´Ç³ú wholemeal flour
1 medium free-range egg, beaten
50g/1¾oz low-fat plain yoghurt