~from Savoring Time in the Kitchen
This makes enough to put together one small Gingerbread House or one Gingerbread Tree
1 large egg white
1⁄2 teaspoon cream of tartar
1-1/2 cup powdered sugar (approximately)
In a large clean bowl, beat egg whites and cream of tartar with electric mixer until blended.
Add powdered sugar about 1/4 cup at a time, mixing on high speed after each addition. Scrape down the sides of bowl as needed.
Keep adding powdered sugar and beating until mixture is very thick but still spreadable. You may use less or more powdered sugar to achieve the desired thickness depending on the size of your egg white.
If not using right away, mixture can be covered tightly and refrigerated until ready to use. Stir thoroughly before using.