Can you use baking powder instead of soda in peanut butter bar cookies?

No, you cannot directly substitute baking powder for baking soda in peanut butter bar cookies. Here's why:

* Different chemical reactions: Baking soda (sodium bicarbonate) requires an acidic ingredient to activate and create bubbles that make baked goods rise. Baking powder, on the other hand, already contains an acid, so it reacts with moisture to produce carbon dioxide.

* Taste and texture: Replacing baking soda with baking powder would likely result in a flat, dense cookie with an off-flavor. The lack of the desired rise would also affect the texture, making the cookies less chewy.

What to do instead:

* Use baking soda as directed in the recipe: Peanut butter bar cookies typically use baking soda because they often include acidic ingredients like brown sugar or molasses.

* Adjust the recipe: If the recipe doesn't contain an acidic ingredient, you can add a small amount of buttermilk or lemon juice to activate the baking soda.

* Leave out the leavening agent: For a dense, chewy cookie, you can omit the leavening agent altogether.

Remember to always follow the recipe instructions carefully. If you are unsure about a substitution, it's best to consult a reliable baking resource or a professional baker.