The other great innovation that northern Europeans, specifically the Viennese, brought to layered pastry was yeast. Both croissant dough and Danish (two of the four main layered doughs, the others being flaky pastry and puff pastry) call for it. That may seem a little odd since as I mentioned, layered doughs already employ steam power, or mechanical leavening to push themselves up. But then where is it written that you can only use one type of leavening per pastry? Quite a few baked goods, especially those in the biscuit family — baking powder biscuits and even pie crusts — use tag team leavening, though in most of those instances it’s a combination of mechanical and chemical leavening (baking soda or powder).
The nice thing about putting yeast in a laminated dough is that it takes a bit of the pressure off the dough maker. Where puff pastry needs many, many well-executed folds or “turns” to create a good rise, croissant and Danish offer a sort of safety net. If you don’t distribute the butter evenly or do the turns perfectly, the Danishes will still rise just fine. Sure, you’ll get a more bread-like pastry versus a flaky one, but it will be every bit as rich, tender and flavorful.