Preheat the oven to 170°C fan. Line a muffin tray with 12 paper cases.
Assemble all ingredients.
Stir the apple cider vinegar into the oat milk and set aside for 3–5 minutes to create a light vegan buttermilk.
In a large bowl, whisk together the flour, rolled oats, baking powder, bicarbonate of soda, salt, hemp seeds, and cinnamon until evenly combined.
In a separate bowl, mash the bananas until mostly smooth. Add the sugar, Irish rapeseed oil, vanilla extract, and the acidulated oat milk, then whisk until fully combined.
Add the wet ingredients to the dry ingredients and fold gently with a spatula until just combined. Avoid overmixing.
Allow the batter to rest for 5–6 minutes to hydrate the oats and hemp seeds.
Divide the batter evenly between the muffin cases, filling each about ¾ full.
Sprinkle the tops with hemp seeds, oats, and a small pinch of cinnamon if using.
Bake on the middle shelf for 22–24 minutes, until domed and springy to the touch.
Cool in the tray for 10 minutes, then transfer to a wire rack to cool fully.
Recipe Notes
Ripe bananas matter: The riper the bananas, the better the sweetness and texture. Well-spotted bananas give the lightest crumb and best flavour.Don’t overmix: Fold the batter gently until just combined. Overmixing will lead to denser muffins.Storage: These muffins keep well for up to 2 days at room temperature and freeze beautifully once fully cooled.