Give the all-purpose cream an overnight refrigerator chill, or place it in the freezer for 30 minutes before starting. The cream should feel thoroughly cold when you pour it.

Peel the mangoes, separate the fleshy cheeks from the pits, and slice them lengthwise with their flat sides against the cutting board. Thin, intact strips will lie flatter between the cracker layers.

Pour the cold cream into a large mixing bowl and, for an optional airier filling, use a hand mixer to increase its volume to roughly double. Leave it unwhipped for a denser filling, or look for a noticeably lighter, fuller consistency when whipping.

Blend the condensed milk into the cream in gradual additions. The finished mixture should look uniform, without separate streaks of condensed milk.

Cover the bottom of the dish with graham crackers, spread one-quarter of the cream mixture across them to the edges, and add mango slices. A continuous cream coating helps the outer cracker corners soften along with the centers.

Continue stacking crackers, cream, and mango until you have four layers, finishing with cream and mango on top. For an overlapping finish, lay the final mango slices partly over one another without piling them into a mound.

Refrigerate the assembled dessert for 3 to 5 hours, allowing longer if the crackers still feel dry, and freeze afterward only if you want a firmer result. Check for plump grahams that yield easily to a butter knife without a dry, crunchy center.