Would this work with an AP flour?

The answer is, yes you can. But to try to get the same consistency would be difficult. They will be bland and crunchier than the buckwheat version. But if you have picky eaters... Girl.. I get it. LOL

There are recipes on the web for a three ingredient brownie made with AP flour, so you could likely substitute it in this recipe. The question is why would you want to? The whole reason for using the buckwheat, or even one of the other whole grain suggested substitutes, was to get a nuttier flavor addition from the flour. You won't get that from AP flour.