In a medium bowl, whisk together the Jello powder and gelatin powder.
Add the boiling water and whisk until everything dissolves
Stir in the cold water.
Pour the mixture into a rectangular dish, cover with plastic wrap, and refrigerate for 4 hours.
To release the jello, submerge the container in hot water for 15-30 seconds. Place a cutting board on top and invert the container. The jello should fall out on its own. Lift the container off and slice the jello into cubes. Enjoy!