Pastel de nata

Pastel de nata is a Portuguese egg custard tart pastry made with cinnamon. Not only popular in Portugal, they are also popular in other parts of Western Europe, Asia and in former Portuguese colonies such as Brazil, Mozambique, Macau and East Timor.
History.
"Pastéis de nata" were created by Catholic monks at the Hieronymites Monastery in Saint Mary of Bethlehem, in Lisbon. During that time, convents and monasteries used egg-whites for starching clothes being part of their religious habits. They also used the leftover egg yolks to make cakes and sweet pastries.
After the Liberal Revolution of 1820 in Portugal, people abandoned religion and closed down many convents and monasteries, the monks started selling "pastéis de nata" to bring in income. In 1834, the monastery was closed and the recipes sold to the sugar refinery owners. In 1837, the super refinery owners opened the Fábrica de Pastéis de Belém and made pastries.
Since the opening of Fábrica de Pastéis de Belém, the original recipe of the pastel de nata is kept as a secret. The recipe is unchanged to this day and is known by very few people. The Fábrica de Pastéis de Belém, remains the most popular place to buy pastéis de nata around Lisbon. The shop is located near the Jerónimos Monastery. 
In 2009 "The Guardian" listed "pastéis de Belém" as one of the 50 "best things to eat" in the world and has over 50,000 reviews and ratings on Tripadvisor for its iconic pastéis de nata.
In 2011, following the result of a public vote, the pastry was announced as one of Portugal's Seven Wonders of Gastronomy, it is one of the country's most popular national dishes.