The original recipe says to use peanut butter and Dutch process cocoa. I just threw in Nutella instead, but I think the peanut butter and cocoa would be yummy too, so I'll probably try that out tonight. I also halved the recipe, and it made plenty for two people. I think you could safely figure on needing one banana per serving.
First, you have to slice and freeze the bananas. I had cut some bananas into chunks and stuck them in the freezer to use for smoothies and they worked just fine, although the original recipe suggests using thinner slices. Once they're frozen you throw them in a food processor and blend away. I have a Ninja Kitchen System and it chopped up those frozen bananas into itty bitty pieces in no time. After that I had a hard time getting the bananas into the whipped stage. The chunks kept getting pressed against the bottom and sides of the blender. Finally I tried using the middle speed instead of the high one, and voila! It whipped my bananas right up. If your food processor gives you grief, just scrape the sides and keep trying, playing around with the speed a little.
Banana "Ice Cream"
adapted from Use Real Butter
2 bananas, sliced and frozen
1 Tbs. Nutella (optional)
Put frozen banana slices in food processor and process until smooth and creamy, like a soft serve ice cream. If desired, add Nutella and blend well.