Can I substitute potato starch (katakuriko) for cornstarch in a cookie recipe?
We keep both in the house, and i always seen to find myself in the middle of prep and not being able to find the one I'm looking for. As a consequence, I have subbed katakuriko for corn starch and vice-versa in equal amounts on several occasions, and never had trouble with the results having the wrong texture or tasting strange.

That being said, I have never used a substantial amount (more than a teaspoon or two) in any recipe, either.