Preheat the oven to 180°C (350°F) or prepare your air fryer.
In a large bowl, combine oats, wholemeal flour, baking powder and cinnamon.
In another bowl, mash the bananas with a fork. Add eggs, vanilla, oat milk and oil. Mix well.
Fold in the ground almonds or walnuts, then gently stir in the blueberries.
Spoon the mixture into 12 silicone muffin cases. Place them on a baking tray or directly in the air fryer basket.
Bake for 20–25 minutes, until golden and firm to the touch.
Cool in the cases for 5 minutes, then transfer to a wire rack to cool completely.