Put the banana, milk, egg and vanilla extract in to the blender. Blend until smooth.
Melt some butter in a frying pan and carefully spoon the mixture in to the pan. I use a ladle and fill it up half way. If you use a cup for measurement then I would say fill it half full. It all depends on how big you like your pancakes.
After initially putting the mixture in the pan I turn the heat down to low so that they cook throughout and don't burn on one side. Keep checking the underneath and then flip them over when you are happy with the colour.
Just a note as a reminder that these are not the crepe style pancakes so I wouldn't spread the mixture too thinly.