1. Peel the mangoes, remove the seeds and puree in an electric blender with the lime juice. There will be 5 cups of purée. Stir in the sugar.
2. Soak the gelatin in 3 tablespoons cold water and dissolve over simmering water. Cool and stir into the mango purée.
3. Beat the egg whites with salt to stiff peaks. Whip the cream until stiff. Fold the cream into the egg whites, then fold this mixture gently into the mango purée. Pour into a large serving dish and refrigerate 2-3 hours.