The exact recipe will depend on the brand of baking powder that you end up buying, but as a general rule, you can expect the ingredients list of this leavening agent to include a mixture of baking soda, cream of tartar, and some form of moisture absorber (for example, corn starch). This behaves in a similar way to yeast, but at a much faster rate, which makes it perfect for use in food that doesn’t contain any acid of its own, like in batter for cookies, cakes, pastries, pies, or quickbread.