Put the biscuits in a freezer bag and crush them with the rolling pin. Line a flat cake tin with half of the biscuit crumbs.
Rub the orange peel and squeeze the orange. You need 4 tablespoons of juice. Separate the eggs, set the egg white aside, you will need it later.
Beat the egg yolks and sugar with a whisk until they are white. Bring the water to the boil, place the mixing bowl with the egg yolk and sugar mixture in the water bath. Beat in the salt and orange juice. Beat in the water bath until the sugar is completely dissolved and the mixture is thick. Fold in the orange zest.
Peel the mango, cut the flesh from the core and cut into small cubes.
Whip the cream and egg white separately until stiff and pull both into the egg cream. Pour the cream evenly over the biscuit crumbs. Spread the mango cubes and the remaining biscuit crumbs evenly on top.
Place the tart in the freezer and freeze for about 4 hours.
Note: If you take the orange biscuit (orange-baked) from my profile, the tart gets a nice note of cinnamon and goes well with the Christmas menu as a dessert.