Start by splitting the icing into two bowls. Leave the white icing in one bowl. In the second bowl, mix in the blue gel food coloring. You’ll need more blue icing than white, so make sure most of the icing goes into the blue bowl.
Spoon all of the white icing into a piping bag with a small #2 decorating tip. You also need to do this with a 3rd of the blue icing.
Put the rest of the blue icing into another piping bag, but this time just cut a small hole at the tip. Set aside.
Use the piping bag with the #2 tip to carefully outline the edges of the cookie with the blue icing. After you’ve outlined the cookie, use the second bag of blue icing to fill in the inside.
Using a toothpick, gently spread the icing to the edges to make it smooth. Allow the cookies to set for about 5 minutes.
Then take the white icing and create diagonal lines. Let the cookies sit for 2 hours so the icing can dry and harden. Enjoy!