Preheat oven to 180 C, 400F, Gas Mark 6
Mix together the flour, sweetner, baking powder, 2 whole eggs and the yolks from the other 2 eggs (reserve the egg whites) until they are well combined
Add the mashed banana and vanilla extract and mix well until combined
Whip the remaining egg whites until they form stiff peaks, this may take a while but make sure they are well whipped or your muffins will be very flat
Once peaks hold themselves, add the egg whites to the banana mixture and gently fold them in until they are combined
Pop the paper muffin cases into your tray and spoon the mixture into your cups to just over half way. You will have some left over to make the last 6 after the first batch has cooked
Pop a few chocolate chips on top of each cake (I popped mine in the mix and they sunk so placing them on to will be better)
Place the try in the middle of your over for 12-15 mins until golden brown, remove and place on a wire rack to cool
Repeat with the remaining mixture for the final 6 muffins
Let them cool (if you can resist eating them) and enjoy!