Cooking Ammonia is a chemical leavener that was used before the advent of baking soda and baking powder.Cooking Ammonia releases gas fast and gives a quick rise to something baking in the oven. It doesn’t need an acid or anything else to react to, the way baking soda does; in fact, it doesn’t react to liquid either, as baking powder does. As Cooking Ammonia only reacts when exposed to high heat, this means that while mixing and preparing something, you don’t have to race it into the oven once the leavener is added.
On the plus side, Cooking Ammonia makes cookies light and crisp, and gives a more open crumb. The downside is that a faint ammonia smell can hang around the baked good.
It is used in some traditional German recipes.
Substitutes
Try using a quantity of baking powder which is double the amount of Cooking Ammonia called for.