With an electric mixer, beat together sugar, shortening, and butter until light and fluffy. Beat in egg and vanilla. In a medium bowl, mix flour, baking powder, and salt, then add to electric mixer until dough comes together. Form dough into a disk, cover, and chill for an hour.
Preheat oven to 400 F. On a floured surface, roll dough out 1/8 inch thick. Cut into heart shapes and place on an ungreased baking sheet. Bake 6 to 8 minutes or until just slightly browned on the edges. Immediately transfer to a cooling rack.
Up to 24 hours before serving: Mix food coloring into frosting for desired effect. Frost cooled cookies and store covered at room temperature. Refrigerate leftover icing. Just before serving, liberally sprinkle cookies with Pop Rocks. (Pop Rocks may melt into the icing over time, reducing the popping effect; they’ll still be delicious!)
*Use any color(s) to mix and match with Pop Rocks flavors for your occasion. Shown: dark pink, light pink, and white icing with strawberry- and cherry-flavored Pop Rocks.
Per serving: 174 calories, 5.5 grams fat (3 grams saturated fat), 29 grams total carbohydrates, 15 milligrams cholesterol, 96 milligrams sodium, 0.5 gram fiber, 1 gram protein.
