In a large mixing bowl, whip the cold heavy whipping cream on medium-high speed for about 3 to 5 minutes until soft peaks form.

Slowly add sweetened condensed milk to the whipped cream while mixing on low speed, then increase to medium until the mixture thickens and forms stiff peaks.

Arrange a layer of graham crackers at the bottom of a 9x13-inch baking dish.

Spread one-third of the whipped cream mixture evenly over the graham crackers.

Layer sliced ripe mangoes on top of the whipped cream.

Repeat layering graham crackers, whipped cream, and mangoes for a second time.

Cover the dish and chill in the refrigerator for at least 6 hours or overnight.

Once chilled, slice into squares and serve.