I grew up eating the Cantonese variation of these egg custard tarts. However, if you want the real thing, you have to go straight to the original source: Portugal. When baked and crisped to perfection, there are very few pastries that can compare. The best ones we had were at Pasteis de Belem. Don't be turned off by the crowd of tourists. It's well worth the wait.
Runner Up: Ichigo Daifuku (strawberry and red bean mochi) - Tokyo, Japan