If using fresh fruit, freeze the strawberries and sliced bananas until completely firm.
Combine the frozen strawberries, bananas, yogurt, and maple syrup in a food processor.
Process, stopping to scrape down the bowl as needed, until the mixture is completely smooth and creamy.
Serve immediately for a soft, sorbet-like consistency, or transfer to a freezer-safe container and freeze until firm. If frozen solid, let stand at room temperature for 5 to 10 minutes before scooping.