My daughter and I have made them several times but generally using fairly hard flours like KA’s bread flour or spelt, which I think may have an even higher protein content than bread flour.
But I ran into this guy just now while googling and although he does not test 100% cake flour, he does do a relatively low protein content croissant using a mix of KA’s AP and cake flours. Also tested were bread flour, all AP, and two French flours (TIL they use a different rating system not having to do with protein) designated as “T45” and “T55”.
The upshot of his testing seems to be that you might get some variation in crumb and/or crust, but they all worked fine (but like I said he didn’t test an all cake flour recipe).
