Preheat the oven to 180C / Fan 160C / Gas Mark 4. Grease a 20cm x 20cm square tin.
Peel the bananas and mash them in a bowl using a fork.
Mix together all the ingredients in a large mixing bowl to form a batter.
Pour into the baking tin and smooth out. Add a couple of extra chocolate chips on top.
Bake for 30 minutes, remove from the oven and cool before serving warm or cold.
Video
Notes
To Store: These can be refrigerated for up to 5 days, and you can also freeze them. I recommend doing this in individually-wrapped portions for easy defrosting.