01 - Combine mashed bananas, whole milk, heavy cream, sweetened condensed milk, granulated sugar, vanilla extract, and salt in a blender. Blend until the mixture is completely smooth.
02 - Transfer the smooth mixture to the Ninja Creami pint container. Seal tightly, place upright, and freeze for a minimum of 12 hours or overnight to achieve proper texture.
03 - Mix graham cracker crumbs, melted unsalted butter, and brown sugar in a bowl using a spoon or spatula until the consistency is similar to wet sand. Set aside for use after spinning.
04 - Insert the fully chilled pint into the Ninja Creami ice cream maker and process on the Ice Cream setting according to manufacturer instructions.
05 - Using a spoon, create a 1-inch well in the center of the processed ice cream. Spoon the prepared graham cracker mixture into the well.
06 - Reinsert the pint and activate the Mix-In function until the graham cracker swirl is evenly distributed throughout the ice cream.
07 - Scoop into bowls. Top with whipped cream and sliced bananas if desired, and serve immediately for optimal creaminess.