Line a brownie tin and preheat oven to 180 degrees celsius.
Place bananas in a high speed blender and blend until it forms a liquid. If you do not have a blender, you can mash it well with a fork.
If your nut butter is firm, i suggest gently warming it to give it a slightly drippy texture to allow it to be easier to stir and combine
Mix the nut butter, oil, egg/flaxegg & vanilla until if forms a wet mixture. Add the rest of the ingredients and combine well.
Place in brownie tin and bake for roughly 20-25 mins until toothpicks come out slightly under.
Leave to cool and slice into brownie squares
Store in an airtight container in the fridge and enjoy!