First time we ever made them. MC was first time I heard of them too. I followed this
https://www.youtube.com/watch?v=CYQpoklVagQ . Although some of the comments indicated they had problems with cooking times, mine timed out perfectly with what he said. I used regular baking potatoes, maybe medium size. They certainly weren't the humongous ones, but they weren't small either. I did take a thin slice off the rounded portion so there would be more of a flat surface on both sides to get more of that nice crusty brown goodness.
We really liked them. Crispy on outside, soft and fluffy on inside. They were kind of like what I do with chunky roasted potatoes by parboiling, drying, then dousing with olive oil on a sheet pan and having to stir as they cook, but only used 1 pan (yeah!) and were overall less work. You do have to get your timing right though because they start to lose the crispness if they have to sit in a warm oven too long. I'm guessing restros probably give them a quick heat up in a pan, basting with butter and/or olive oil to get the crispy back.
I saw recipes that used either rosemary, sage, or thyme, or some combinations thereof, as well as smashed garlic.