01 - Whip the chilled heavy cream using an electric mixer on medium-high speed until soft peaks form.
02 - Gently fold the sweetened condensed milk into the whipped cream until thoroughly blended and smooth.
03 - Arrange a single layer of graham crackers in the bottom of a 9x13-inch glass dish, breaking pieces as necessary to fit the surface.
04 - Spread one-third of the cream mixture evenly over the graham cracker base.
05 - Distribute one-third of the sliced mangoes over the cream layer in an even arrangement.
06 - Repeat the layering process twice more: graham crackers, cream mixture, then mangoes, ending with mangoes as the final top layer.
07 - Sprinkle graham cracker crumbs over the top surface if a textured garnish is desired.
08 - Cover the dish securely with plastic wrap and refrigerate for a minimum of 6 hours or overnight until completely set.
09 - Cut into squares while cold and serve immediately. Garnish with fresh mint leaves if preferred.