01 - In a blender, combine mashed bananas, whole milk, heavy cream, sweetened condensed milk, granulated sugar, vanilla extract, and salt. Blend until completely smooth.
02 - Pour the banana mixture into the Ninja Creami pint container. Seal and freeze upright for at least 12 hours or overnight until thoroughly frozen.
03 - In a small mixing bowl, combine graham cracker crumbs with melted unsalted butter and brown sugar, stirring until the mixture resembles wet sand. Set aside.
04 - Once fully frozen, place the pint container into the Ninja Creami and process using the 'Ice Cream' setting.
05 - After the initial processing, create a 1-inch well in the center of the ice cream and add the prepared graham cracker crumble.
06 - Reinsert the container and process with the 'Mix-In' function until the swirl is thoroughly incorporated.
07 - Scoop into bowls and top with whipped cream and sliced bananas if desired. Serve immediately for optimal texture.