Using your electric mixer with the whisk attachment, add the mashed banana, sugar and Greek yogurt. Mix until incorporated.
Add melted butter, eggs and vanilla extra and mix.
Add flour, baking powder, baking soda and salt to the batter and mix until just incorporated. Do not over mix!
Using a spatula, fold in the chocolate chips.
Scoop the batter into a zip lock bag and seal shut. Using scissors, snip the bottom corner of one side of the ziplock bag to create your homemade piping bag.
Grease your doughnut baking pan and pipe 3/4 full the batter into each doughnut mold.
Optional: Sprinkle cinnamon and sugar mixture on top of each doughnut batter before baking. Or you can dip the doughnuts once baked in the cinnamon sugar mixture. You may need to paint melted butter on top of each doughnut before dipping the doughnuts in the sugar mixture to allow them to stick. Both options work perfectly.
Bake for 12 to 15 minutes. Remove from the pan and allow to cool before eating.