Use this icing as the glue for your gingerbread house and accompanying decorations. It dries hard as a rock in just a few hours. Since it includes raw egg whites, don't eat this stuff. Nobody wants Salmonella for Christmas!
4 egg whites
4 cups powdered sugar
1t. lemon extract or lemon juice
Beat all ingredients at low speed until icing forms peaks, 7-10 minutes. Cover bowl with a wet towel while you work or (better yet) move directly into an airtight container. Use decorator bags and tips or a cookie press to pipe icing onto your gingerbread masterpiece.