How much baking powder & baking soda do I need to use for my cocoa cookies? How much baking powder &amp; baking soda do I need to use for my cocoa cookies?
Based on the following recipe that does not contain egg, and makes use of both types of cocoa powder. I am trying to get the crunchy and airy texture.
200    grams  all purpose flour
 10.5  grams  natural cocoa powder
 10.5  grams  Dutch process cocoa powder
  0.5  gram   ammonium bicarbonate
  1.3  grams  salt
  0.2  gram   vanillin    
113    grams  sugar
 61    grams  butter
You don't strictly need to use any leavener in this type of cookie. You can certainly get a firm, nonchewy texture without it, although it is unlikely to be &quot;crunchy&quot; and not very airy - it is more sandy, melts-on-the-tongue thing. Of course, if you use crystal sugar (as opposed to powdered sugar) you will experience some crunch from the non-melted sugar crystals, which might be what you wanted.
If you want to try a leavener, a typical amount would be 1 teaspoon (around 5 g) of baking powder for 250 g of flour. Use that as a starting point for the recipe development - I don't think you have to reduce it to 4 g from the start, since 1) traditional recipes are not that accurate anyway, and 2) the cocoa powder also adds starch, which kinda &quot;counts as flour&quot; for the purpose of calculating leavening. There is no reason to use any baking soda. And of course, remove the ammonium bicarbonate - if you really want to experiment with a combination, do it after you have created a working simpler version of the recipe with just baking powder.