Baking powder, I remember reading somewhere, is NOT good for Yorkies! I will try to find the source for you, but it's really not good for them at all. (they included it along with the dreaded chocolate, raisins, onions, etc.)
Okay here it is:
http://www.petplace.com/dogs/dangero...dog/page1.aspx Baking Powder and Baking Soda. Baking soda and baking powder are both leavening agents. A leavening agent is a common ingredient in baked goods that produces a gas causing batter and dough to rise. Baking soda is simply sodium bicarbonate. Baking powder consists of baking soda and an acid, usually cream of tartar, calcium acid phosphate, sodium aluminum sulfate or a mixture of the three. Ingestion of large amounts of baking soda or baking powder can lead to electrolyte abnormalities (low potassium, low calcium and/or high sodium), congestive heart failure or muscle spasms.
I'm not sure exactly what "large amounts" entails. You might be alright if you're just adding a teaspoon of powder to a large batch of cupcakes.