Thus armed, tackling the recipe itself an elemental combination of confectioner's sugar, flour, eggs and anise oil is easy. (You may have most of the ingredients on hand already.) For leavening, purists prefer a pinch of hartshorn (aka baker's ammonia), which is traditional in Scandinavian baking and thought to produce a tender, fluffier crumb but conventional baking powder more than suffices.

WSJ: Wunderbar Christmas Cookies