Thinly slice bananas; transfer to a large resealable plastic freezer bag. Arrange slices in a single layer; freeze overnight.
Pulse bananas in a food processor until finely chopped. Add yogurt, maple syrup and raspberries. Process just until smooth, scraping sides as needed. Serve immediately, adding fresh berries if desired.
Chocolate-Peanut Butter: Substitute two tablespoons each creamy peanut butter and baking cocoa for the raspberries; proceed as directed.