On Eastlake, there is a magic window through which you can see what appear to be blocks of butter the size of old-school computer monitors sitting on a long wooden table. That's exactly what they are: 50-pound butter bricks. The smell from the street: flour and butter and sugar, so sweet and rich it almost hurts. The window belongs to 15-year-old bakery Le Fournil, and their pastry case contains all manner of croissants—plain, chocolate, almond, raisin, raspberry, peach, ham and Swiss—as well as tarts, éclairs, and other glistening pastries, each berry or slice of fruit in place, all resting 20 feet from the oven that baked them.

I meet owner Nicolas Paré, who still makes every baguette himself, to find out how they make those luscious croissants. Originally from Nantes, France, Nick apprenticed as a baker at 14 and has been baking ever since. "I can't do anything else," he says, laughing. (His accent is exactly what you'd hope.) The croissant process takes nearly a week and is one he learned in New York, where the chef told him, regarding baking processes (and, probably, life): "If something works, don't change it." First, the dough, whose ingredients Nick counts off: flour, water, milk, salt, and yeast ("not much!"). Then it goes into the freezer. A few days later, around six in the evening, it'll come out to rise overnight, reaching readiness at 4 a.m. On the table in front of us, a baker runs the dough back and forth through a roller into a long thin rectangle. Then he takes a slab of butter the approximate size of a smallish coffee-table book, places it in the middle, and folds the dough over it like a present. They'll do this folding a few more times, letting the dough rest in between, until it's layer after layer of dough and butter. It goes back in the freezer for a few days.

Make a little "C" with your thumb and forefinger—that's how big the frozen unbaked croissants are. In the bakery, row after row of their risen but unbaked siblings await the oven. Raspberry jam oozes out the sides of some, chocolate batons peek out the ends of others. They're fat, and you can see all those layers that were so lovingly folded into being.

In the cafe, I select a peach and a chocolate croissant. They're rich and soft, and little flakes explode all over my sweater with each bite. I pick off every last one and eat it.