PORTLAND, Ore.—Purim isn't the Jewish calendar's biggest holiday, but it may be the tastiest, celebrated with the hamentasch, the traditional three-sided pastry made with a variety of sweet fillings.

It is a treat baked to resemble the tri-corner hat worn by the villain in the Purim legend, "Haman the Agagite," who the Old Testament says was thwarted in a plot to murder Jews in Persia in the 5th century B.C. Since then, untold millions of hamentaschen have been consumed by Jews world-wide during Purim, which is celebrated...