In a high speed blender or food processor, add your frozen banana and blend until smooth. Add the cocoa powder and blend once more, until fully incorporated.
Transfer the low calorie ice cream mixture into a freezer friendly container and store in the freezer for at least two hours, to freeze. For the first hour, stir the mixture every 20 minutes, to ensure it doesn't become icy.
Remove the container from the freezer and let it sit at room temperature for 15 minutes, before scooping and serving.
TO STORE: Low calorie ice cream should always be stored in the freezer, covered. Be sure the container is freezer friendly to ensure it does not get freezer burns. The ice cream will keep well for up to 1 month.TO SERVE: Let the ice cream thaw for 15 minutes before serving.