Preheat oven to 200 degree C / 400 degree F. Line a baking pan with muffin cups.
Measure all DRY ingredients to make muffins (all-purpose flour,whole-wheat flour,rolled oats,sugar,baking powder, baking soda, salt)
In a medium size bowl, mix together all DRY ingredients.( DRY )
Measure all WET ingredients to make the muffins ( egg,milk, mashed bananas, oil, vanilla extract)
In a large bowl, beat the egg lightly. Stir in milk, oil and vanilla extract.
Add the mashed bananas and combine thoroughly. (WET)
Using a spatula add the DRY flour mixture into the WET banana mixture.
Stir until JUST mixed. Do not OVERMIX or the muffins will become tough.
Using an ice-scoop spoon the batter into the muffin cups.
Bake in preheated oven for 15 minutes.
When baked, remove baking pan to cool on rack for 5 minutes.
Transfer baked muffins from pan to cool further on a wire rack.
And you're done! Serve baked warm muffins on serving tray. Enjoy!