Preheat the oven or air fryer to 180°C. Line a small square baking tin with baking parchment or prepare a silicone mould that fits your air fryer.
Mash the bananas and blackberries together with a fork until mostly smooth.
Stir in the grated apple, oats, vanilla extract and ground ginger until well combined.
If the mixture seems too wet, add a little extra oats or a couple of Tbsps of ground almonds or chopped walnuts.
Spoon the mixture into the prepared tin or mould and spread it out evenly.
Bake in the oven for about 25 minutes, or until the top is lightly golden and the mixture is set.
Alternatively, bake in the air fryer for about 18 minutes.
Leave to cool in the tin or mould before transferring to a wire rack. Once completely cool, cut into slices.