How to Make It
Set a fine mesh strainer over a medium bowl. Pour in the oranges and reserve the juice. You should have about 1 cup of juice and 2 cups of fruit.
In a medium heatproof bowl, sprinkle the gelatin over 1/3 cup of the reserved juice. Whisk gently until the mixture starts to thicken. Add the boiling water and whisk until smooth. Stir in the remaining 2/3 cup of juice along with the mango nectar. Pour 3/4 cup of the gelatin mixture in each of 4 glasses. Refrigerate until the mixture is thick and syrupy, about 1 hour. Spoon 1/2 cup of the drained oranges into each glass and refrigerate until set, about 4 hours. Serve cold with whipped cream, if desired.