Recipe: Banana and Nutella Muffins

I made these little beauties for my friend's charity cake sale - she will be hitchhiking to Croatia in a couple of weeks all in the aid of charity! I thought I'd help her out in the way I know best - baking!
Banana and Nutella are a match made in heaven, perfect on pancakes. I thought i'd try them out in cake form. This recipe calls for those really ripe bananas, the ones going brown and mushy on the windowsill.