How much baking powder & baking soda do I need to use for my cocoa cookies?
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.