The Mexican sweet bread topped with a shell-like sugar crust is called a concha.
A concha is a small, soft, enriched bread covered with a patterned paste made from sugar, flour, and fat. The topping usually forms ridges resembling a seashell, which explains the Spanish name concha, meaning “shell.” Common flavors include vanilla, chocolate, and sometimes strawberry.
Conchas are a classic part of Mexican pan dulce, or sweet bread. They are commonly eaten at breakfast or with coffee and hot chocolate, and bakeries often sell them in several colors and flavors. The bread itself is not filled; its distinctive feature is the crisp, sweet topping.
Conchas are sometimes confused with other Mexican sweet breads because pan dulce includes many shapes and recipes. Their shell pattern and separate sugar crust are the clearest identifying traits.