These are a traditional Jewish or Israeli cookies associated with the holiday of Purim. The name translates to Hamen's hat or Hamen's pockets or Hamen's ears in Hebrew. The three-cornered shape refers to the shape of Hamen's hat. You'll see three different fillings traditionally: poppy seed, apricot and prune. These will keep one week in an airtight container. They also freeze well.
To make the Filling: Place the ingredients in a saucepan and bring to a boil. Reduce heat and simmer for about 15 minutes or until soft and the liquid is absorbed. Add water, if needed. Let cool.
To make the Dough: Combine the flour, baking powder and salt in a food processor. Add the butter and pulse. In a small bowl, mix together the sugar, egg, egg white, and orange zest. Add it to the processor and pulse to mix, being careful not to over mix. Divide into 2 disks and chill 30 minutes.
Preheat oven to 350 degrees F.
Roll out the dough on a floured work surface to 1/4-inch thick. Cut out 2 1/2 to 3-inch disks. (You can re-roll the scrapes to make more disks.) Place a disk of dough down and place 1 teaspoon of filling in the center. Pinch the disk in 3 places to form a triangular shape with the filling still showing in the center. They will look like 3 cornered hats. Place 2 inches apart on baking sheets. Continue until all the disks are made.