Once you unlock the condiment stand, you can plant and harvest soybeans and wasabi root to elaborate sauces for some of your recipes. If you produce soy and wasabi seasonings and can't find where to use them, tap on your kitchen stands to find which recipes will include these elements in the elaboration. 

 

 

 

For example, if you tap on the MAGURO NIGIRI in the dialog window, you will find that there's a soy sauce unit among its ingredients. You should go to the research section to be able to offer this specific nigiri if you want to use your soy sauce!