Pasteis de Nata, deliciously soft, sweet, custard tarts, are a cult in Lisbon. And one place is the undisputed master of making them. In Belem, just off the waterfront, is the Antiga Confeitaria de Belem - a blue and white-tiled temple to eggs, cream sugar and pastry. Their 170-year-old recipe is of course, a guarded secret, divulged to only three chefs at any one time. The result is delicious - perfectly browned, with individualism catered for with sachets of icing sugar and cinnamon. Turning out 16,000 tarts a day, and every one hand-made, this is worth a trip to Portugal alone.