Martha Stewart has one of our favorite royal icing recipes. You can find it here.
For the polka dot cookie, create a dam around the outside of the cookie and then flood it with whatever matching color you like. Shake and tap your cookie to get out any air bubbles. Next use a small circular tip to create polka dots. Then add your favorite sprinkles.
For the plaid cookie you will need 3 colors of frosting. First start with your background color. Create a dam and then flood the entire cookie with your base color. Next, use your darkest color and draw two lines horizontally. With the lighter color draw 4 lines on each side of those. Let it dry for a minute. Then add two stripes of the darkest color vertically. Surrounded by stripes of the lighter color. And there you have it, a perfectly plaid heart cookie!
We hope this little video helps!