Preheat your oven to 175 degrees Celsius
Mash your bananas. I do this in a Thermomix but you can usea food processor, an hand mixer, or even a fork.
Add the butter and sugar and beat until smooth.
Add the eggs and vanilla and beat again for about 10 seconds, or until combined.
Add the rest of the ingredients and mix until smooth, but don't over beat.
Pour into 12 muffin cases or into a loaf tin. If you are cooking muffins you'll need to cook for about 20 minutes. Test the inside with a fork or skewer to make sure they are cooked through before removing. If you are cooking a loaf, cook for an hour. Test before removing.