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 a Ninja Creami pint container. Seal tightly and freeze upright for a minimum of 12 hours or overnight.
03 - In a small bowl, mix graham cracker crumbs with melted butter and brown sugar. Stir until the mixture takes on the consistency of wet sand. Set aside.
04 - After freezing, insert the pint container into the Ninja Creami and select the 'Ice Cream' function for processing.
05 - Make a 1-inch well in the center of the ice cream base. Fill the well with graham cracker crumble.
06 - Reinsert the container and process with the 'Mix-In' setting until the graham cracker swirl is evenly distributed.
07 - Scoop prepared ice cream into bowls. If desired, garnish with whipped cream and sliced bananas. Serve immediately for best texture.