I won't take credit for this by any means, I found it here. Genius!
You will need:
2 packages of unflavored gelatin
4 (or 5) 3 oz. packages of different flavored/colored Jell-o
1 can of sweetened condensed milk
Here's what ya do:
1) Prepare all your Jell-o according to the package, only use ONE cup of boiling water, instead of two.
2) Allow your Jell-o to "chill out" in the fridge for AT LEAST 4 hours.
3) Pour half a cup of cold water on top of the 2 packs of gelatin in a small bowl. Allow it to sit for 4 to 5 minutes. In the meantime, boil 1 cup of water. When water has boiled, add to the sitting gelatin. Then pour in your sweetened condensed milk. Stir until it is all dissolved and more fluid like. Let cool until room temperature.
4) Precisely cut your Jell-o into cubes. Combine all cubes in a glass dish.
5) Once milk/gelatin mixture has become room temperature, pour over your Jell-o cubes. Some will float to the top, and that's ok! Just make sure they're not completely sticking out of the top.
6) Let sit in the fridge overnight.
7) Cut into squares. Or use cookie cutters to cut out neat shapes!
Looks just like a mosaic, huh? But a delicious, edible one. Yum!