An egg-and-cheese croissant all too often involves an overdone fried egg and a bland slice of Swiss wedged into a too-chewy pastry. At Portland’s Belleville bakery, the pastry that goes by that name is something else entirely. The croissant-making process at Belleville is so labor intensive, it spans three days. Day one: work the dough to just the right texture. Day two: fold and shape it into layers. Day three: for the egg-and-cheese variety, make a hole in a 4-by-4-inch piece and bake for precisely 17 minutes. Finally, baker Chris Deutsch cracks an egg into the hole, tops with provolone and rosemary, and gives a quick finish in the oven. The golden-brown pastry frames a shimmering, shimmying yolk — it would look equally at home in an art gallery as a bakery case. Gossamer layers of buttery dough yield one by one and meld with the yolk, sharp cheese, and piney herb. So wonderful is every last flake that whenever I have one, it pains me to brush the crumbs off my clothes after.