Mae Sai: they were roasting chestnuts all over town

They were put in a large wok with lots of small black rocks over a flame. When the nuts were deemed finished, they used a metal spoon with large holes to sift out the rocks. We aren't sure where they got the rocks from - maybe from the river bottom? (yum!) Regardless, it was a good system. We sampled some when we were trying to figure out what they were and they weren't all that tasty, so we didn't invest in a giant bag. Note: We have never seen, nor tasted a roasted chestnut in the States, so this is all guesswork.