Let's be honest—royal icing is not known for being delicious. At best, it's a sweet and simple paint for rolled sugar cookies, but at worst, it's little better than Elmer's glue. Even so, bakers come back to this classic icing time and again, because it's as easy to make as it is to use, and it guarantees a gorgeous, smudge-proof facade for decorated cookies.
Typical recipes involve two parts egg white to nine parts sugar by weight, a ratio that ensures this ultra-low-moisture icing can dry to a crisp. Given that it's mostly sugar by weight, it's important to acknowledge that royal icing is, by nature, pretty dang sweet. There's no point in denying it, but that doesn't mean royal icing lacks the capacity to evolve.
First and foremost, making the switch from conventional to organic powdered sugar will instantly give royal icing a greater depth of flavor. That's because organic powdered sugar still contains a portion of its natural molasses content, so, instead of tasting like pure sucrose, it has the mellow sweetness of raw cane sugar.
Most organic powdered sugars are also made with tapioca flour rather than cornstarch, which reduces the sense of grittiness in royal icing. The downside to organic powdered sugar is that the presence of molasses gives the icing a decidedly ivory hue, so it may not be the best choice for super-snowy designs or light pastels. But when the icing is tinged with bright and vibrant primary colors, that off-white shade is easy to overcome. (More color comparisons and information on conventional versus organic tapioca-based powdered sugar can be found in my article on the subject.)
Another simple way to improve classic royal icing is to make sure it's well seasoned. When making a sauce, chefs always work to ensure it has the right salt, acidity, and aromatics to bring out its best flavor, and I feel it's important to treat royal icing the same way—at least, if you plan on eating it. Obviously, that means starting with plenty of salt to tame the icing's sweetness, but also adding a bright burst of acidity. For me, that means cream of tartar, which has a neutral flavor that won't interfere with whatever cookie I have planned. A splash of vanilla extract is a no-brainer for almost any type of frosting, but less intuitive is a spoonful of silver rum. Made from cane sugar, rum has a natural affinity for dessert, adding a sense of richness and complexity without darkening the icing, as most other spirits would.
Royal icing is typically a raw preparation, with everything just mixed up in a bowl, but I've found it has a much creamier consistency if cooked over a water bath. Not only does this technique ensure the powdered sugar is fully dissolved, and therefore less gritty, it effectively pasteurizes the egg whites, too. I, being both callous and cavalier, have no qualms about raw-egg icings (their extremely low-moisture/high-sugar formulation makes it nigh-impossible for bacteria to thrive), but for many, this extra step can lay the fear of raw eggs to rest. Plus, you get a creamier royal icing with the ingredients you have at home already—no special-ordering meringue powder or pasteurized eggs.
If you're actually concerned about raw eggs, cook the royal icing to 150°F (66°C) over a water bath, and hold it there for three minutes. If you're more inclined to live on the edge, simply cooking until it's hot to the touch is more than enough to ensure the powdered sugar has thoroughly dissolved.
Once the icing's hot, I add a bit more powdered sugar to thicken things up. It dissolves with the residual heat of the icing, and saving it for last keeps the icing thin and easier to stir while it's over the water bath. From there, I beat the royal icing until it's thick, light, and perfectly creamy.
The goal of this process is to ensure the royal icing is silky-smooth, not to whip it up like cream; excessive aeration would only introduce pesky air bubbles that would later pock your ideally smooth icing. For that reason, creaming with the paddle attachment is vastly preferable to whipping with a whisk (although, if need be, you can certainly make do with a hand mixer set to low speed).
At this stage, the royal icing is thick enough to handle chunky designs (like the buttons on a gingerbread man, or little rosettes on a cake), and it's also the least messy option if you plan to decorate some cookies with the kid. But if you'd like to glaze the tops of cookies with an even sheen of royal icing, or attempt a more ambitious, elegant design, it needs to be thinned first. Thinning the icing makes it much more difficult to work with, a recipe for disaster for small children still honing their fine motor skills. So, please bear in mind: Thinned royal icing should be limited to use by teenagers and adults.
Most recipes rely on water to thin royal icing, but I've found cream to be far superior. To continue my analogy regarding a properly made sauce, a small amount of cream adds richness, improving the flavor and mouthfeel of the icing all around. Since fat carries flavor, it also enhances our perception of vanilla, so the icing seems more aromatic as well. These subtle improvements work together for an icing that seems less sweet, as verified through several blind tastings among my friends.
We're not talking a lot of cream; just three tablespoons in a two-and-a-half-cup batch. If that's a problem, try using plain, unsweetened, full-fat coconut milk instead. Of course, water will do in a pinch, but it's not a 1:1 swap, so take care when experimenting on your own, adding less at first and then thinning as needed from there.
The only downside to the addition of cream is that the icing may curdle if mixed too long. Fortunately, that's only a risk if you leave the icing on the mixer unattended (a technique some bakers use to keep royal icing from crusting over in the bowl).
Properly thinning the icing with cream is largely a matter of precision measurements, but unless you start by beating an egg white to weigh out a hyper-specific amount, there will always be an element of personal judgment in determining whether the icing is too thick or too thin. The process becomes intuitive when you've done it countless times before, but here's the test I use at home.
Lift up the beater and drizzle the icing back into the bowl, making a figure 8 pattern. If the figure 8 is still sitting there after eight seconds, the royal icing is too thick, and your designs may be lumpy. If the figure 8 melts away much more quickly, the royal icing is too thin, and your designs will run and drip. To adjust, simply stir in a few drops more cream to thin, or another teaspoon of powdered sugar to thicken, repeating (or alternating between the two) until the figure 8 disappears into the surrounding icing after exactly eight seconds. It can be a bit of a cereal-and-milk situation, going back and forth a few times, but with patience, you'll get it just right.
When royal icing can hold its shape for eight seconds, it's said to have a "flood consistency," a particular stage that allows royal icing to both outline and fill a shape. It's this unique viscosity that lets professionals glaze an intricately shaped cookie without any drips.
Once it's adjusted to flood consistency, my royal icing can be divided into as many as four bowls to color with gel paste—liquid dyes will throw off the consistency too much. (To get really fancy, you can even add a pinch of pearl dust to give it a subtle shimmer.) If you'd like more colors, I'd recommend making a double or triple batch, or else the quantity of each color will be less than half a cup, which isn't much if you've got a lot of cookies to frost. As with any recipe, use caution when multiplying each ingredient for a larger batch, as even one small error will derail the icing.
If you've divvied up the icing to color, cover each bowl in plastic wrap to prevent it from crusting over when not in use; royal icing can begin to dry within 60 seconds, especially around the edges of the bowl, where splashes let it spread out thin. After coloring the icing, transfer it to a parchment cone or a disposable pastry bag coupled with a super-fine tip (I use Wilton #3). It may be tempting to just drop the tip in the bag and be done with it, but with royal icing, I recommend using couplers, which make it easy to remove and clean the piping tips should they become clogged by a wayward flake of crusty icing.
Bagging the icing minimizes its exposure to air, so you don't have to worry about it crusting over, and reduces the risk of a messy spill or just accidentally jabbing your finger in the bowl. (Like paint, dyed royal icing has a way of getting everywhere if you're not paying attention.) If you wanna get fancy with cookie decorations, check out my Royal Icing Tutorial for more photos, videos, and ideas.
So preheat that oven, start rolling out those sugar cookie cutouts, put on your favorite elf hat, and let the holiday baking begin!