Lisa, I have a pain de mie recipe that calls for potato flour. I can't get potato flour in my area and I'd rather not mail order it. One of the staff bakers at King Arthur flour told me I could substitute ground up instant mashed potato flakes. That's what I've been doing. I have an electric coffee grinder I use for other tasks - no coffee grinding - and use that to "whizz" up a good quantity of potato flakes until they resemble flour. Works perfectly. You might try that.
Thank you, Katie E. The idea of the potato flakes was an inspiration while at the supermarket. I was going to use my processor,but, since I have an extra coffee grinder also, which I've used for spices, I try that. Thanks, again for the tip. Have a Merry Christmas (or Happy Holidays). LisaD