This is your BFF when building a gingerbread house. It dries like a rock and makes the daintiest little icicles. —molly yeh
Test Kitchen Notes
The sole expectation of gingerbread house icing is that it be edible glue, and Molly Yeh’s version here rises to the occasion. Take a cue from Erin McDowell’s gingerbread house guide, and make alternate cookies to eat while you build.
While most royal icing recipes call for the addition of egg whites, fewer call for stiffly-beaten egg whites, and fewer still call upon the stabilizing powers of cream of tartar. When egg whites are beaten, air bubbles get introduced into the liquid. The proteins in egg whites are forced to denature and rebuild as a webby network between the introduced air bubbles. Cream of tartar works by stopping these protein networks from growing too strong and close together. This is why cream of tartar often appears in recipes where stiffly-beaten egg whites are too—it allows whipped egg whites to become their most voluminous and elastic selves (as opposed to clumpy and dry).
Maybe you’re wondering: What’s egg white volume and structure got to do with gingerbread house icing? A puffy icing that’s structurally sound, like Molly’s version, swells into gingerbread nooks and crannies with ease, and can build upon itself to create structural, decorative elements ("daintiest little icicles," indeed). Because of the cream of tartar, the icing remains supple as it dries, so it won't crack.
If you’d like to add flavoring or extract, add it after the egg whites have whipped, with the machine running on low (mix until it just disappears).
As Erin mentions in her guide on how to build a stunning and stable gingerbread house: Grab a friend to build with you. Having a second set of hands to stabilize walls when you attach the roof (or need a cookie break) makes the whole process even more enjoyable. —Coral Lee
Watch This Recipe
Gingerbread House Icing
enough for 1 house and a ton of decorations (or a few houses and a few decorations)
In a large bowl or the bowl of a stand mixer fitted with a whisk attachment, beat together the egg whites and cream of tartar until foamy. Gradually beat in the powdered sugar. Beat on medium high for 7 to 10 minutes, until very fluffy.
Immediately spoon into a piping bag and use. Any frosting that's not being used should remain under plastic wrap (the plastic wrap should touch the surface of the frosting), so that it doesn't dry out.