Preheat oven to 176℃ | 350℉. Grease 2x 12 hole donut pans with a thin layer of spread of choice (butter/margarine or coconut oil). Wipe over excess with a paper towel.
Whisk together the sugar, oil, butter (or spread) and egg until light and creamy. Add in in the banana, vanilla and cinnamon and whisk again until combined..
Add the flour(s), salt, baking soda and powder, mixing together until just combined (do not over-mix the batter).
Fill donut pans 1/2 way using a teaspoon (about 1 1/2 teaspoons of batter per donut hole). Using 1/3 cup pre-melted Nutella, pour 1 teaspoon Nutella per donut over the batter in the pans. Carefully cover each donut with remaining batter, using your fingertips if you need too, to make sure there is a secure 'lid' over the tops.
Bake in preheated oven for 10-12 minutes, or until puffed and golden brown, and set to the touch (they should spring back when pressed down). Allow to cool for about 5 minutes before removing from pan.
While donuts are baking, prepare toppings:
Toppings:
Whisk cream cheese and sugar in a bowl until thick and creamy. Mix in the vanilla (as much as you like) to suit your tastes.
Prepare a shallow bowl with the cinnamon sugar. While the donuts are still warm, transfer four (or more/less) donuts to the cinnamon sugar mix and turn to coat evenly.
Frost another four (or more/less) with the cream cheese frosting. And spoon the remaining Nutella over the top of the remaining donuts. Enjoy!
Please Note:
To make donut holes, fill a mini muffin pan half way with batter. Spoon 1/2 teaspoon Nutella onto the centre, and top with about 1 teaspoon of batter, or enough to cover. To bake, follow the instructions above.