Preheat the oven to 350 degrees.
Prepare the sugar cookie mix according to the instructions on the package.
Place a thin dusting of flour down on the counter, and roll out the dough to about ¼ of an inch thick.
Press the different sized cookie cutters into the rolled out batter firmly. You will need one heart of each size for each cookie that you wish to make.
Place the cut out hearts on a cookie sheet lined with parchment paper or a silicone baking mat.
Bake the cookies for 9-11 minutes, until they are cooked through and slightly browned on top.
Let the cookies cool down completely.
Starting with the largest sized heart cookie, place a layer of cake frosting on the front of the cookie.
Apply one type of Valentine colored sprinkle to the frosted cookie, and set down.
Take the next largest sized heart shaped cookie, and apply frosting to the front of it as well.
Coat that heart cookie with the next color of Valentine colored sprinkles.
Apply a dab of frosting to the bottom of the medium sized heart cookie, and press it down onto the center of the larger sized heart cookie that you already coated in sprinkles.
Take the smallest sized heart shaped cookie, and apply frosting and sprinkles to it as well.
Apply a dab of cake frosting to the back of that cookie, and press it down onto the top of the other two to finish creating your heart stacked cookie.
Repeat steps 8-14 until you have finished creating all of your cookies.
Let the frosting harden to hold the cookies together, and then serve.