They're based on a traditional Dutch speculoos cookie, and their genius is in their simplicity. The dough is straightforward, doesn't rise much, and is mostly spices: cinnamon, cardamom, cloves, ginger, nutmeg - all the good Christmas-y (or St. Nicholas-y) ones. They taste warm and comforting, and are one of the few cookies I prefer crunchy. They beg to be eaten with coffee or tea. Especially at 20,000 feet up in the air.
I've followed a great recipe in one of these cookbooks that comes close to reproducing them. But there's just something about flying in a plane that, ahem, elevates the whole experience. While the wrapper is still intact, I snap the cookies into thirds, and savor each bit with my nose pressed against the window. Perfect.