Peel bananas and slice them about 1/2" thick. Lay the slices on a sheet pan lined with parchment paper and place it in the freezer for a minimum of an hour until they are frozen.
Place frozen banana and mango chunks in a food processor. Do not use a smoothie blender as it will not blend properly
Once the fruit is crumbled, add soymilk or other plant milk and vanilla (and maple syrup if using). Process until smooth, stopping to scrape the sides from time to time. The consistency should be thick like a soft serve ice cream.
Eat immediately or transfer to a freezer safe container for future use. If freezing, take it out 15 minutes prior to eating to let it soften.
Serve with toppings of your choice.
Serving size is about 1/2 cup. Nutrition values do not include optional maple syrup. If using maple syrup, calories are 69 per serving and 2 g of added sugar (12 g total sugar)