Materials needed: mini star cookie cutter, square cookie cutter (mine is 2 ¼ inches), sugar cookie dough (my recipe here) chilled and rolled out, royal icing in red, white, blue, and yellow (see my favorite recipe here), pasteurized egg whites, plastic or parchment paper piping bags (I use parchment paper), pastry tips #1.5 or #1, medium paintbrushes, a sharp knife, and several small bowls.
Step 1: Make the cookies:
Use the cookie cutters to cut out star and square shapes from the rolled dough. To create the firecracker, use a sharp knife to divide the square cookies into rectangles. Place the rectangles onto a parchment-lined cookie sheet, leaving space around each one for a star-shaped cookie to be added. Use the star cookie cutter to cut off the end of the rectangle. Then carefully fit the cut end of the rectangle in between two points of the star cookie and press together lightly so that all edges are touching. Using your finger, gently shape the bottom corners of the rectangle to create a curve. This is a little tricky, so be sure to look at the photo of the cookies on the tray to see how to do it.
Bake the firecrackers at 350°F until the edges are slightly brown, about 10-12 minutes. Remove from the oven and let cool completely on the tray. Do not handle the cookies before they are fully cooled.
Step 2: Prepare the icing:
Prepare four small bowls of icing in red, blue, white and yellow; you’ll need more of the red and blue icing, and much less of the white and yellow. Add egg whites gradually to thin out all the colors to the consistency of toothpaste or slightly thicker. Fill individual piping bags fitted with pastry tips. Use about half of the red and blue icing and all of the white and yellow. Add a little more egg white to the bowls of red and blue, thinning the icing to the approximate consistency of maple syrup. This “flooding” icing will be used to paint within the piped outlines. Be sure to cover each bowl of icing with plastic wrap so no crust forms.
Step 3: Decorate the firecrackers:
Pipe a line of red icing around the outline of the star but leave a space open where the rectangle and star connect (see photo). With a paintbrush, carefully fill in the outline with red icing, thinning out as you approach the lower rectangular area that will be the blue firecracker (see second photo). Let dry completely, for about four hours. Use the bag of blue icing to pipe the outline of the firecracker, drawing a cylindrical top shape within the red star. This will overlap the thinned-out area of red icing. Flood with blue icing and let dry completely, about four more hours. Re-outline the firecracker with blue. Pipe a double outline of white icing around the points of the star and then add the tiny white wick. Use the yellow piping bag to pipe a spark at the end of the wick. Decorate with red and white stripes or tiny sparks!