In the bowl of a food processor, combine the flour, salt and sugar. Cut the frozen butter or margarine into cubes and spread over the flour mixture. Pulse a couple of times until there are no longer clumps of butter, and the mixture resembles coarse breadcrumbs.
Add the egg yolks and three tablespoons of ice water, and pulse until the mixture comes together as a dough. If the dough appears too dry, add up to 1 additional tablespoon of ice water. Do not over-work the dough or the texture will get messed up.
Divide the mixture in half, and place each half in a plastic bag in the refrigerator for at least a couple of hours, up to overnight.
To assemble the Hamantashen:
Preheat oven to 400 degrees. Line a cookie sheet with parchment paper and set aside.
In a small bowl, combine all filling ingredients except for the nuts. Whisk to combine. Add the nuts and stir them into the mixture.
Roll out the chilled dough on a lightly floured surface to about ¼ of an inch. Cut out circles of dough and set aside. Repeat with all dough, then reroll the scraps and cut more circles.
Spoon a small amount of the filling (about a teaspoon) into the center of a dough circle. Be careful not to get too much of the liquid, or it will drip out and cause the hamantash to open while baking. (At the end you may be left with some liquid from the filling.
Lift up three sides of the circle, joining them in the center to form the hamantash shape. Squeeze the edges to keep them from opening.
Beat the egg white lightly until foamy. Brush the beaten egg white along the seams to keep them from opening during baking.
Place the hamantash on the prepared tray and repeat with remaining dough circles.
Bake at 400 for 12-13 minutes, until golden.
Recipe by Overtime Cook at https://overtimecook.com/2014/02/17/pecan-pie-hamantashen/