While we’re substituting…

To make your own baking powder add 1/4 teaspoon baking soda and 1/2 teaspoon cream of tartar for every 1 teaspoon of baking powder your recipe calls for. Best to add them in separately, since it would be a shame if they were to start reacting prematurely. You can make your own supposedly-storable baking powder by adding another 1/4 teaspoon of cornstarch, but…why?