I made mango ice box cake instead of tart because it is easier to prepare. Line an 8 x 8 inch square glass container with whole, not crushed, fat free honey graham crackers. For the cream: refrigerate ½ can of fat free condensed milk for 2 hours. Beat powdered egg whites, equivalent to 4 whites, until stiff, sprinkle 2 tablespoons sugar and continue beating for 2 minutes, set aside. In another bowl, beat ½ cup heavy cream until it holds its shape, gently fold in egg whites. Whip cold condensed milk for 2 minutes, then gently stir into cream mixture, add 1 cup chopped mango pulp. To assemble: Spread cream mixture on top of graham crackers. Top with mango balls. Freeze until almost firm. Thaw slightly before serving.
Variation: Use sliced peaches (in jar not canned), drained and sliced very thin, in place of mangoes.