Where to find the best pasteis de nata in Lisbon

If chocolate on the pillow is a universal sign of a fancy hotel, a plate of fresh Portuguese custard tarts on the bedside table is proof of an extraordinary one. I'm in Lisbon, capital of Portugal, where the custard tart is king. At Four Seasons Hotel Ritz Lisbon, a freshly-baked trio of the irresistible treats awaits my arrival. Frankly, I have never enjoyed a welcome amenity more.

Known locally as pasteis de nata, the bite-sized flaky pastries filled with rich custard are one of Portugal's most famous exports.

Served warm or at room temperature, they're often dusted with cinnamon and eaten as a sweet snack with coffee or tea.

Nobody is exactly sure who made the first tart and why, but we thank them nonetheless. Many believe they originated in the Jeronimos Monastery, a World Heritage Site (and resting place of Portuguese explorer Vasco da Gama) in the Lisbon riverside district of Belem, when 18th-century monks were experimenting with ways to use up leftover egg yolks.

The egg whites were in hot demand as a starch agent for their white habits.

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Today, the tarts are sold in supermarkets, bakeries, cafes and specialty stores all over Portugal, and in many other countries.

There's heated debate over who makes the best in Lisbon. Pasteis de Belem, Manteigaria and Confeitaria da Gloria are strong contenders. At locations around the city, lines snake out the door from morning until late at night, seven days a week.

I gaze with wide eyes at the selection on display in the window of Pastelaria Ferrary on Lisbon's Rua Augusta. In addition to the classic custard variety, there's a Nutella version, mango and lemon temptations, and several kinds of nut-flavoured tarts.

For six euro ($10), I buy six fresh tarts, packaged snugly in a cardboard sleeve for easy transportation. That is, if I have the willpower not to eat them all today.