Place the cream in a bowl, and mix it until it is smooth and not lumpy. Add the condensed milk and fold using a spatula.
Put some of the cream mixture in the tray and spread evenly.
Place a layer of Graham crackers (without overlapping) to cover.
Put some cream on the Graham and spread evenly.
Last some thinly sliced mangoes as close to each other as possible.
Place a layer of cream and spread.
Repeat step 4 until you run out of mango slices.
Top with crushed Grahams.
If you have extra slices but not enough to cover another layer you can put them on top of the Graham bed.
Place in the freezer to set.