Visitors flock to see the mosaic tiling and waterways that earned Aveiro the nickname “the Venice of Portugal.” But this city has a flavor all its own, which is—in large part—egg yolk. Ovos Moles, wafer confections filled with sweet, vibrant yolk, are a symbol of the canal-lined, coastal city.

Housed inside delicate wafers shaped like whelks, fish, and starfish, the rich, sweet filling harkens back to the origins of ovos moles as a convent sweet. After using egg whites to iron their habits, nuns were left with an excess of egg yolks. They relied on sugar, readily available in Portugal by the 16th century, to extend the shelf life of the surplus of perishable egg product.

In 1834, Portugal began to extinguish religious orders. The last living nuns were tasked with the final operations of their convents, after which, the establishments would permanently shut down. In Aveiro, the last nun at the Monastery of Jesus de Aveiro passed away on March 2, 1874. After that day, bakeries took over production of ovos moles, which remained a beloved treat in the region. Today, you’ll find them in confectioneries all over the bustling city.