Q: Isn't the whole point of Passover food that there was to be no leavening? Isn't baking powder and baking soda leavening?
A: The K for P baking powder contains no corn starch, which regular baking powder does contain. In Biblical terms, leavening required a fermentaition process, which is achieved with yeast. Baking powder does not use a fermentation process, it's a chemical process, and not forbidden. Some people feel torn about using the K for P baking powder, and it is hard to find. I have one very old recipe I use yearly which requires it. I've really only seen it in a few published recipes. I'm guessing that's because it's nearly impossible to get your hands on unless you live near a store with a VERY well stocked K for P section.