2 bananas, mashed, plus 1 banana, cut into 12 slices
Preheat the oven to 200°C (400°F), Gas Mark 6. Line a muffin or cupcake tray with 12 paper cases.
In a large bowl, combine the flours, oats, sugar, baking powder and cinnamon.
Measure the milk in a large measuring jug and whisk in the egg yolks, oil, coffee, and mashed bananas. In a clean bowl, whisk the egg whites until they form soft peaks.
Make a well in the centre of the dry ingredients and pour in the contents of the jug. Using a spatula, mix together until just combined. Fold through the egg whites, then divide the mixture amongst the paper cases.
Push a slice of banana into the centre of each muffin and sprinkle with oats. Place in the oven to bake for 25 minutes until golden on top.
Remove from the oven and allow to cool slightly before transferring to a wire rack to cool completely. The muffins will keep for 4–5 days in an airtight container or for up to 3 months in resealable bags in the freezer.