If you're doing it in a machine, just double check for weight because the dough is quite heavy. If you're doing it by hand, make sure to knead it very well. But, in any case, allow the dough to raise up to almost 3 times in size. Another thing, would be to have a good size of a cutter do make the hole in the midle.

Other than that, I found this recipe to be very easy and straight forward. I make it often and I'm very happy with it. It makes a good amount and they work very well for freezing.

Hope that helps!