Use this as a substitute for baking powder: Keep this tip handy for all the baking you're bound to do in the next few months. Most bakers know that baking soda and baking powder are not interchangeable. They work their magic in different ways depending on the recipe. But if you find yourself unexpectedly out of baking powder, you can add a couple of things to baking soda and use the combination to get by. For every 1 teaspoon of baking powder called for in a recipe, combine ¼ teaspoon baking soda, ¼ teaspoon cornstarch and ½ teaspoon cream of tartar and use that mixture instead.
Michelle Stark, Times food editor