Preheat oven to 180°C/350°F fan oven and line a baking try with baking parchment.
Mash bananas with a fork and mix with the peanut butter and maple syrup if using.
In another bowl mix all the other dry ingredients apart from the raisins. Add in the banana and peanut butter mixture and mix well. Distribute on the baking tray and bake for 20-25 minutes. Stir through in between. Take out and leave to cool. Mix with the raisins.
Store in an airtight container.