Making the icing

Place the water and meringue powder in the bowl of a stand mixer or a large mixing bowl. Using the whisk attachment or an electric mixer, beat ingredients together until powder has dissolved and mixture has become very foamy.

Add the powdered sugar gradually and mix slowly at first to avoid a snow shower.

When sugar is incorporated, raise speed to high and mix until icing is bright white, smooth, glossy, and the consistency of toothpaste.

Using the icingWhat happens next depends upon how you'd like to use your royal icing. If you plan to do a lot of fine detail decorating, or if you're brand new to the line and flood technique, it's a good idea to create two different thicknesses of each color — one for lining and details, one for flooding. The icing that you have right now should be a good consistency for lining and details, but depending on environmental factors, you may want to add a bit more water. If it seems too thick to comfortably squeeze out of a piping bag, go ahead and whisk in more water a tablespoon or two at a time until it's reasonable to work with.

If you're a little more comfortable with piping, and/or if you plan to create mostly patterned decorations in a single layer, you can use a single, thinner consistency for all of your decorating. In my environment in the wintertime, flood icing usually requires up to a full cup of water (total). Proceed slowly until you learn what works for you.

Transfer a small amount of the icing to a smaller bowl and mix in a few drops of the color you'd like to use to line your cookies. Spoon this icing into a disposable piping bag and snip off a tiny bit of the bag's tip. Draw a line of icing as close as you'd like to the outer edge of your cookie, making sure to connect the line's ends to each other so the flood icing won't have any gaps to flow out.

In another small bowl, mix some more of the icing with a few drops of the color you'd like to use to flood your cookies, along with two additional teaspoons of water. This icing should be thin enough to spread slowly and slightly across the surface of the cookies, but no thinner than that. You may need to experiment a little to find the consistency that's best for your humidity and, ahem, skill level. Pour this icing into another piping bag or better yet a squeeze bottle.

Squeeze some flood icing onto the surface of a cookie, filling in the entire surface inside the line. You can use a toothpick to fill any gaps that don't fill themselves and gently rap the cookie onto the work surface if you're brave and want a perfectly smooth finish.

Depending on the look you're going for, you'll either wait for the first coat to dry (for about an hour) before proceeding, or add decorations right away. For textured icings with multiple layers, let the base coat dry first. If you plan to swirl or otherwise incorporate additional colors into a single layer, or add sprinkles or other decorations, do it right away.