What you need:
Packet/Boxed Sponge Mix
Mash the bananas and stir in 2 beaten eggs. Add the cake mix and give it a good mix, then add a couple of spoons of Nutella and mix well before spooning into a mini muffin cake tray and baking in a preheated oven (gas 4) for around 15-20 minutes, until a skewer poked into the centre of the muffins comes out clean. Leave to cool before eating. These will store in an airtight tub for a couple of days, around a week in the fridge or you can freeze them for up to 4 months and take out as you need them.
Before freezing allow the muffins to cool completely and wrap each muffin tightly in cling film to lock in freshness wrap several times for the best protection. Put the wrapped muffins into a large freezer storage bag for an added layer of protection. Remove the muffins individually as needed, leaving the remaining muffins in the freezer, this means they are great for packed lunches too because you can remove a single muffin in the morning, and it should have thawed in the lunchbox by lunchtime, but maybe do a sample check first, we don't want little ones eating half frozen muffins do we!