Last time I looked, L’epicerie sold French flours, and the times I have ordered from them they have been very helpful and knowledgeable. But mail order can sometimes be a bit too much to go through for ingredients. The two US flours that I’ve tried that are very extensible are KAF’s Italian style flour and GM’s Better for Bread. They have vastly different protein contents, and the Italian is also mail order, though I happen to have a good stock of it at the moment for special pizza nights.
If I were to make a go of Kouign Amann today, I would probably mix some of the Italian style into the BB to bring down the protein a bit and help keep the dough from becoming too elastic. And I’ve always been tempted, with laminated doughs, to try a test bake where the dough was just mixed and autolysed in the fridge overnight (like pain l’ancienne), then let the lamination folds take care of building the rest of the structure.
Vermont Butter & Cheese makes a cultured high-fat euro style butter than I use for lamination, it is very nice. But I live in New England, not sure if it is available on your coast.
Must say I was surprised, even shocked, at the way the man in your video link dumped a boatload of sugar onto the dough. I had always envisioned careful, thin layers of sugar so as not to risk messing up the lamination.
Hope you’ll post a pic of your result!