Add Food Coloring
Make a St. Patrick’s Day treat out of crispy rice bars using a shamrock cookie cutter and green food coloring. You can also use green Peeps or green marshmallows if you can find them. However, the easiest way to make these green bars is to use white miniature marshmallows and food coloring.
Add the green food coloring into the hot melted marshmallows. Gels or liquid dye will easily mix into the hot mixture. Start with 2 or 3 drops and add more if you want a darker green bar. You can vary the shade of green by adding either a drop of yellow or blue food coloring to the green color. Stir until the mixture is a uniform color.
Add the Cereal
Add the cereal and mix well to coat all of it with the green marshmallows. Then pour it into a large butter-greased pan. A shallow sheet pan with sides works best because its shallowness helps keep the cereal from being too thick, making it easier to cut with the cookie cutter.
Use Parchment Paper
The best way to spread out the sticky cereal bars is to place a sheet of parchment paper over the cereal. Then press with your hand or a large spoon, and the cereal mixture will spread without sticking. Spread the mixture to 1/2-inch depth for even bars. It is okay if the mixture doesn’t cover the whole sheet pan, but keep the edge 1/2 inch thick. Then cut the cereal mixture with a shamrock cookie cutter.
Sometimes it helps to grease the cookie cutter with butter to help it cut through the cereal. Use a small folded towel to help press the cookie cutter through the cereal mixture if you don’t have one with a “comfort” grip.
Re-Form Leftover Scraps
Re-form all the leftover scraps again and cut shamrocks out of them. Be careful not to press the cereal too hard when reforming it, or you will crush it, making smooth-looking bars. You can eat these bars yourself because they taste the same. Enjoy!