01 - Place mashed bananas, whole milk, heavy cream, sweetened condensed milk, granulated sugar, vanilla extract, and salt in a blender. Blend on high until completely smooth.
02 - Pour blended mixture into the Ninja Creami pint container. Seal tightly and freeze upright for at least 12 hours or overnight.
03 - Combine graham cracker crumbs, melted unsalted butter, and brown sugar in a small bowl. Stir until mixture has the texture of wet sand. Set aside.
04 - Once base is thoroughly frozen, insert the pint container into the Ninja Creami machine. Process on the 'Ice Cream' program.
05 - After the initial cycle, create a 1-inch well in the center of the ice cream. Fill the well with the prepared graham cracker crumble.
06 - Return the pint to the Ninja Creami and use the 'Mix-In' setting to gently incorporate the graham crumble throughout the ice cream.
07 - Scoop ice cream into serving bowls. Top with whipped cream and sliced bananas if desired. Serve immediately for optimal creaminess.