Dashi stock is a type of stock that is in the form of a powder. It can be added to miso soup or clear soups for extra umami flavor. In this Japanese okonomiyaki recipe, dashi adds lots of that Japanese-inspired flavor, but if you don't have it or can't find it, simply omit it! However, if you choose to omit it, make sure to add a pinch of salt to the batter instead.