If you don't have an ice cream maker, chop the banana into small chunks and freeze beforehand. When blending everything, do it really thoroughly to get lots of air in, then pour into a suitable container and freeze for about 2 hours.
Texture won't be quite as good, but taste will be the same.
I've tried all sorts of flavours in me ice cream maker, but this is the best so far.
posted by Ronny/Capybara Moonc