- Preheat the oven to 160°C. Grease and line a 25cm loaf tin with baking paper.
- Beat the butter and sugar until light and fluffy, add eggs one at a time, beating well after each. Stir through the yoghurt, baking soda and the mashed banana. Mix in the flour, protein powder and lastly the walnuts.
- Spoon the batter into the prepared tin and bake for 30 minutes before increasing the heat to 180°C. Bake a further 30 minutes or a skewer inserted into the middle of the loaf comes out clean.
- Allow to cool in the tin for 10 minutes before turning out onto a wire rack to cool completely. Store in an airtight container.
* Toast thick slices of day old banana bread and serve with extra yoghurt and chopped walnuts.