01 - Combine mashed bananas, whole milk, heavy cream, sweetened condensed milk, granulated sugar, vanilla extract, and salt in a blender. Blend until completely smooth.
02 - Transfer the blended mixture into the Ninja Creami pint container. Seal tightly and freeze upright for a minimum of 12 hours.
03 - In a small bowl, thoroughly mix graham cracker crumbs with melted butter and brown sugar until the mixture resembles wet sand. Set aside.
04 - After the base has frozen solid, insert the pint into the Ninja Creami device and run the 'Ice Cream' function.
05 - Form a 1-inch well in the center of the ice cream with a spoon. Add the prepared graham cracker crumble into the well.
06 - Reinsert the pint and process on the 'Mix-In' setting until the swirl is fully incorporated.
07 - Scoop ice cream into bowls. Add whipped cream and sliced bananas as desired. Serve immediately.