- Prepare the mangoes: Peel the mangoes and slice them thinly. Set aside. 
- Whip the cream: In a large bowl, whip the chilled heavy cream to soft peaks. Slowly fold in the sweetened condensed milk until smooth and creamy. 
- Layer the dessert: In an 8x8-inch glass dish, arrange a layer of whole graham crackers to cover the bottom. 
- Add cream: Spread a layer of the whipped cream mixture evenly over the graham crackers. 
- Add mangoes: Arrange a single layer of mango slices over the cream. 
- Repeat layers: Continue layering graham crackers, cream, and mangoes until the dish is filled, ending with a cream layer on top. 
- Top with garnish: Garnish the top layer with sliced mangoes arranged decoratively and a sprinkle of crushed graham crackers. 
- Chill: Cover with plastic wrap and refrigerate for at least 6 hours, preferably overnight, to let the layers set and soften. 
- Serve: Slice into portions and serve chilled.