Preheat oven to 180°C. Grease mini muffin pan or line with paper cases. Melt butter and cool.
Sift flours into a bowl and mix in oats. Stir to combine. In another bowl, mix honey, melted butter, milk, egg and mashed banana. Pour this mixture into the centre of the flour mixture and stir until just combined. Spoon into muffin pans and bake for 30-35 minutes until golden and a skewer inserted into the centre comes out clean. Cool slightly, then place on wire rack to cool completely.
Muffins can be frozen for up to two months. No need to reheat. Just thaw and serve.
The butter can be substituted for 60ml of macadamia or vegetable oil. I prefer to use butter as it tastes better and when thawed, is more moist.