In a small bowl, sprinkle 2 packets of unflavored gelatin over ½ cup of cold water. Let it sit for about 5 minutes to bloom.
Meanwhile, boil 1 cup of water.
After blooming, pour the boiling water over the gelatin and stir until dissolved.
Stir in the whole can of sweetened condensed milk.
Let the mixture cool to room temperature before pouring it over the blue layer.
When it’s cooled carefully pour a layer of the white mixture over the set blue Jell-O, filling another third of the cup. Pop them back in the fridge for another 2-3 hours, until that layer is set too.