At first glance, Pastelaria Alcôa, a bakery in the charming little town of Alcobaça, Portugal, looks thoroughly modern. Behind a gleaming glass counter are colorful, award-winning pastries that have made the pâtisserie one of the most celebrated in the country. On warm days, customers sit outside at tables shadowed by large umbrellas and enjoy the view: a sumptuous Gothic monastery. Alcôa’s specialities are made inside the bakery, but their roots are in buildings like the nearly 1,000-year-old religious institution across the street. In fact, the pastries are prepared precisely in…