Preheat oven to 190°C (370°F) or 170°C (340°F) for fan-forced ovens. Line a standard 12 hole muffin tin with muffin paper cases/liners and lightly spray the inside of them with oil.
Peel and roughly chop the bananas into little cubes.
For the dry ingredients - Place flour, oats, raisins, sugar and salt into a large bowl. Then sift in (or whisk) the cinnamon, baking powder and bi-carb. Mix well to combine.
For the wet ingredients - In a separate bowl, whisk together the buttermilk, olive oil, egg and vanilla extract.
Make a well in the centre of the dry ingredients, then pour in the wet ingredients. Stir 3 times, then add in the banana. Stir a few more times just until combined and there are no dry parts showing. Take care not to over-mix the batter as this will make the muffins dense.
Fill the batter in each muffin hole to the top because these muffins won't rise that much during baking. Bake for 20 to 22 minutes or until a skewer comes out clean when inserted in the middle. Leave the muffins in the tin for 5 minutes, then remove and place on a cooling rack.
Notes
(NOTE 1) Bananas - We won't be mashing the bananas to incorporate in the batter for this recipe, so we don't need overripe bananas. Use just ripe or a little overripe but firm bananas, so they're able to hold their shape when mixed into the batter. We want chunks of bananas in the muffin!(NOTE 2) Plain flour (all-purpose flour) does not have any leavening or raising agents (baking powder) mixed into the flour.(NOTE 3) Rolled oats (Old-fashioned oats) are made from husked oat groats that are steamed and flattened. They're lightly processed and highly nutritious.(NOTE 4) Buttermilk - No buttermilk in your fridge? Make buttermilk substitute by mixing 1 cup of milk with 2 tablespoons of vinegar or lemon in a jug. Cover and refrigerate for at least 30 minutes, the milk should thicken slightly. Give it a quick stir before using.Leftovers - Allow the muffin to cool completely at room temperature. Transfer the muffins into an airtight container and store them at room temperature for 2 days (if not humid). Muffins stored in the fridge will last for 5 days and will freeze for up to 3 months.A Third-Party Application calculated the calories and nutritional information. Please use this as an approximate guide only.Cooking measurements are in Australian standard spoon and cup measurements.