Preheat oven to 180ºC. Line a 12 hole muffin tin with silicone or paper liners.
Place sugar into Thermo bowl and mill 10 sec/speed 10.
Add butter, egg, bananas, vanilla, salt, baking soda and powder and blend 10 sec/speed 6. Scrape down sides of bowl and lid.
Add flour and blend 12 sec/Interval.
Add chocolate and blend 4 sec/speed 6.
Divide batter between muffin holes and bake 18 minutes or until puffed and golden.
Best eaten on the day they are made.