Spray a 8 x 8 pan with nonstick cooking spray.

Pour the Jell-0 into a large bowl, add 2 cups boiling water, and stir until dissolved. Pour into the pan and place in the refrigerator for 2 hours.

In another bowl, add 1/4 cup cold water. Sprinkle the gelatin packet over it and let it stand for several minutes.

Stir in 3/4 cups boiling water and sweetened condensed milk until well combined. Allow cooling.

Invert the red Jell-O pan onto a cutting board or wax paper.

With a heart cookie cutter, cut hearts out of the jello. Cut as many as possible, but you may not use them in the next step.

Spray the pan with cooking spray again. Arrange the hearts in the pan, carefully leaving room for white in between each.

Pour the condensed milk mixture around the hearts and place in the refrigerator for several hours until firm.

Remove from pan and cut into squares.