Three cornered cookies usually filled with fruit representing Haman's hat.

a delicacy! A three cornered cookie filled with prune butter (lekvah) or jam or raisins and .... enough already. It was thought to resemble the hat that the no-goodnik Haman wore. In Israel it's called oznai haman, or Haman's ears. Take your pick. But both are yummy. p. 162

Triangular shaped cookies, traditionally filled with poppy seeds, prunes or a variety of fruits. They are eaten at Purim and were named after the three-cornered hat of the evil ruler Haman.

A hamantasch is a cookie in Jewish cuisine recognizable for its 3-cornered shape. It is eaten during the Jewish holiday of Purim. Traditional fillings are poppy seeds (Yiddish mon) or prune, but they are made with many different flavors, including nut, date or apricot.