This right here? This is why I lugged around a Champion Juicer from San Francisco to Virginia, back to San Francisco, and finally to Portland. The good news is you too can make banana soft-serve with a food processor or good-quality blender.
This treat was whipped up for a discerning 5-year-old and her 10-year-old sitter/friend who proclaimed it the best ice cream she'd ever had! And the only ingredient is frozen bananas.
I've topped it with a homemade chocolate sauce (a bit of cocoa powder mixed with agave), and beautiful raspberries from our yard. Serious yum!
For step-by-step instructions on how to make soft-serve in your food processor, I recommend you look at these from Gena at Choosing Raw.
