The conchas at Mexico City's Rosetta bakery are quilted in dark, chocolate-sugar diamonds. The rolls are dense but somehow airy; yeasty, but not too chewy or sweet. On a recent visit, I gobbled almost en entire chocolate concha before my coffee had even arrived. The secret to these conchas is slow fermentation and a small amount of yeast, which creates a soft, airier crumb, says chef and owner Elena Reygadas, who was hanging out at the bakery recently and answered a few of my questions. “We don’t put a lot of butter,” Reygadas says. “We want to respect the Mexican village-style bread.” Mexico City is undergoing a bakery renaissance, and Rosetta -- a sister establishment to the Rosetta Italian restaurant a block away -- is among those leading the pack. The narrow, warm Colonia Roma cafe invites you to sit and stay awhile. Creamy subway tile covers the walls, and fresh-baked loaves stack neatly inside wooden crates. (One of those loaves is pan de pulque, which is a rare find in Mexico City.) Croissants and chocolatínes mingle in a glass display case near the entrance, along with bulbous popovers bursting out of their little accordion-shaped paper cups. The overall effect is sort of European. But due to the small, sausage-shaped size of the place -- the bakery was once the driveway and garage of a fancy Roma mansion -- it's also quirky, pleasantly chilango. Get there by 8 a.m. on a weekday to snag one of the spot's few coveted seats and to try the conchas. (At 10 a.m. one morning, they'd already disappeared.) The shop's vanilla conchas also contain real vanilla bean. Reygadas admitted it was a little expensive, but I'm hoping she continues to spoil her customers. Rosetta Bakery (the sign says simply "Panadería) Colima 178-A, at the corner of Orizaba Colonia Roma Read about my other Concha Taste Tests in Mexico City here.