Soften the 3 gelatin sheets in cold water. Peel the 3 mangoes and remove the pits. Purée the flesh in a blender, then gently heat in a saucepan. Stir in the drained gelatin until dissolved, and let cool.
Whip the liquid cream into stiff peaks in a large bowl, gradually adding the powdered sugar and vanilla sugar. Fold gently into the cooled mango purée. In a shallow dish, mix the rum with 20 cl water. Quickly dip 12 biscuits in the mixture and line the sides of a 1L charlotte mold vertically. Pour in the mango cream, press down firmly, and top with the remaining 3 biscuits. Refrigerate for at least 3 hours to set.
To serve, slice the remaining mango. Sauté the slices in a pan with butter and icing sugar for 2 minutes until caramelized.
Unmold the charlotte onto a serving platter, dust with icing sugar, and artfully arrange the caramelized mango slices on top.
Pro tip from our kitchen: Pair with passion fruit coulis and fresh mint or lemon balm leaves for an extra burst of flavor.
