I got delayed on this post when I realized that I had no idea what a #medieval #baker used in place of #bakingPowder. It turns out it's "#hartshorn", which is actually the horns of male red deer, dried at high heat and then ground down to a powder.

The ammonia that's part of the active ingredient wafts away during the cooking, making your #kitchen smell terrible. For the few #baking products that still require the airy #leavening it produced, modern bakers use something called #BakersAmmonia.