Salt of Hartshorn

Originally made from the ground antlers of reindeer, this predecessor of modern baking powder is now made with ammonium carbonate. It is commonly used in Scandinavian countries to produce light biscuits with a crisp texture, such as springerle and gingerbread. However, as it can have an unpleasant ammonia flavour, it is best used in biscuits and pastries that are small enough to allow the ammonia odour to disperse whilst baking.