Cut each banana into 6 chunks and freeze until rock-solid, preferably overnight.
Make the ice cream: Put the banana chunks in a food processor and process. (Hang on, your food processor may jolt in the very beginning!) The bananas will look crumbly at first, then gooey and eventually light and creamy, just like ice cream. Stop the food processor frequently to scrape down the sides of the bowl and break up any clumps. Serve right away or scrape into a container and freeze until ready to serve.
Make the sundae: Mash the raspberries and maple syrup together in a small bowl with a fork until saucy. Scoop the banana ice cream into a dish and top with the raspberry sauce, blueberries, pistachios, coconut, chocolate chips and a dollop of Greek yogurt.
Copyright 2016 Television Food Network, G.P. All rights reserved.