For best results, store these cookies tightly covered.
BAKING POWDER AND BAKING SODA Baking powder is a combination of baking soda and an acid, such as cream of tartar. When mixed with liquids, baking powder releases carbon dioxide gas bubbles, causing breads, cakes and cookies to rise. The most common kind of baking powder is called double-acting, which begins releasing gas bubbles as soon as it becomes wet and releases still more when it is exposed to oven heat. To determine if baking powder is still active, add 1 teaspoon to 1/3 cup of hot water. If it bubbles vigorously, it will give good leavening results.
Baking soda is used when an acidic ingredient such as buttermilk, yogurt or molasses is also being used in a recipe. When baking soda and the acidic ingredient combine, carbon dioxide is produced, causing the dough to rise. Because baking soda reats immediately when moistened, recipes using baking soda should be baked immediately.