Chill a mixing bowl and beaters for about 10 minutes. Then whip the cold heavy cream on medium speed until soft peaks form.

Gently fold in the sweetened condensed milk and vanilla extract into the whipped cream until smooth.

Spread a layer of the cream mixture across the bottom of an 8x8-inch dish.

Layer the graham crackers on top of the cream layer.

Add another layer of the cream mixture on top of the graham crackers.

Arrange thinly sliced ripe mangoes over the cream layer.

Repeat the layering process with graham crackers, cream mixture, and mango slices, finishing with a cream layer.

Sprinkle crushed graham crackers on the top cream layer.

Cover tightly with plastic wrap and refrigerate for at least 6 hours or overnight.

Slice and serve chilled.