This recipe had a large error. The amount of liquid to dry ingredients was off (by a lot). I believe it needed to start with 3 times the butter. However, it included an egg yolk, which I haven't seen in any other recipes, so I'm not sure how that affected things.
Regardless, it was overmixed, as I had to keep adding more and more water (before I realized the fault was a lack of butter), and very tough.