A great dessert for 4th of July and the colors can be changed for any holiday is broken glass jello. The recipe is all over the internet but I believe it was originated by the Food Librarian.
6 ounces (one big 6-oz box or two small 3-oz boxes) of "Red" Jell-O such as strawberry, cherry, raspberry, strawberry banana
6 ounces (one big 6-oz box or two small 3-oz boxes) of "Blue" Jell-O
1 (14 oz.) can sweetened condensed milk (don't get evaporated milk)
2 envelopes unflavored gelatin (that Knox stuff) (each envelope is approximately 1/4 ounce)
4 cups boiling water (for colored blocks)
1/2 cup cold water (for milk mixture)
2 cups boiling water (for milk mixture)
Step One: Making the Blocks
In separate bowls, dissolve the Red and Blue Jell-O in boiling water by adding 1 cup of boiling water to 3 ounces of Jell-O. Therefore, you'll need a total of 2 cups of boiling water for the 6 ounces of Jell-O (one big box or two small boxes). Mix to dissolve and pour into a container and chill until firm (overnight is probably best, but I have chilled it 3-4 hours until firm).
Note: Only add 1 cup of water per 3 ounces of Jell-O. Ignore the instructions on the box of Jello (they say to use 2 cups of water per 3 ounces). You need to use less water so the Jell-O is firm and can be cut into blocks.
Step Two: Cutting Blocks and Making the Milk Mixture
Prep a 9 x 13 pan by wiping a very, very thin layer of flavorless oil (such as canola) in the pan with a paper towel. You'll wipe off 99.9% of the oil...leaving just a very, very thin film.
Cut chilled colored Jell-O into small blocks.
Carefully mix the blocks in a 9 x 13 pan.
In a separate bowl, add 1/2 cup cold water. Sprinkle 2 envelopes unflavored gelatin on top of the cold water. Wait a few minutes for the gelatin to bloom (soak up some of the water), then add 1 1/2 cup boiling water and mix to dissolve. Add the can of condensed milk. Stir and cool. Pour cooled milk mixture over Jell-O. If you wish, skim off any bubbles from the surface of the Jell-O. Chill overnight until set.