Pre heat Air-Fryer for 5 minutes at 200°C.
Cut filo in half length-ways. Brush melted butter in between 2 sheets. Brush plenty more on top.
Place 1 piece of Mars Bar on one end of the filo with a piece of banana on top of the Mars.
Roll up "samosa style" until you have a triangular parcel. Brush generously with melted butter.
Cook 2 at a time in the Air-Fryer (depending on the size of your Air-Fryer) for 6 minutes at 200°C.
Serve dusted with icing sugar and loads of Ice-cream.