I already use buttermilk powder for recipes calling for buttermilk and I love it because I never use up all of the fresh buttermilk when I buy it. (foodstoragemadeeasy.net)
The original recipe called for baking soda so I left it in when I added the baking powder and from what I can tell, these cookies are just right. (mymothersdaughter.net)
Lots of recipes call for butter and sugar, but the quantity of each depends on what you're baking. (moneysense.ca)