Peel and slice bananas, place them in a freezer bag and freeze for at least 4 hours.
Place frozen banana slices in a food processor and pulse until they become crumbly. Add almond milk, cinnamon, and vanilla. Continue to blend, 1 to 2 minutes, until the mixture becomes very creamy, like soft serve ice cream.
Scrape down the sides of the bowl as needed. Serve immediately for best results or freeze in an airtight container.
Before serving, let ice cream soften at room temperature. Whip in the food processor until a creamy consistency is formed again.