Peel the mangoes and slice them into thin strips or small cubes. The thinner the slices, the neater your layers will look. Place them in a bowl and set aside. If using frozen mangoes, make sure they’re fully thawed to avoid excess liquid.
Take a chilled mixing bowl and pour in the heavy cream. Whip it using a hand mixer until soft peaks form. This usually takes 3–5 minutes with a mixer or 5–7 minutes by hand. Make sure not to overwhip, or it will turn grainy.
Slowly add condensed milk into the whipped cream while continuing to mix. Taste and adjust sweetness with sugar if needed. Add vanilla extract at this stage for extra flavor. The cream should be smooth and fluffy.
In your baking dish, arrange a single layer of graham crackers. Break pieces if necessary to cover the bottom completely. This acts as the crunchy foundation of your dessert.
Spread a layer of cream over the crackers, about 1/4 inch thick. Place sliced mangoes evenly on top of the cream layer. Make sure every bite gets both cream and fruit.
Add another layer of graham crackers, followed by cream, then mangoes. Continue until you use up all ingredients, finishing with a cream and mango topping.
Cover the dish with plastic wrap and place it in the refrigerator. Chill for at least 4 hours, but overnight is best. The longer it chills, the better the crackers soften and blend with the cream.
Once set, slice into squares and serve cold. Each slice will reveal beautiful layers of mangoes, cream, and crackers. It’s best enjoyed fresh from the fridge on a warm day.