Step 1

Combine the confectioners' sugar, flour and salt in the bowl of a food processor fitted with the metal blade. Process for 10-15 seconds to combine. Add the butter and pulse until the mixture resembles coarse meal. Add 2 of the egg yolks and pulse a few times, until the mixture is crumbly and pale yellow. Add 1 tablespoon of the water and pulse just until the dough starts to clump together. If the mixture seems dry, add the remaining tablespoon of water and pulse again. Dump the dough onto a lightly floured work surface and knead a few times into a smooth ball. Divide in half and pat into two 6-inch discs; wrap in plastic and refrigerate for 30 minutes.

Step 2

Preheat oven to 375°F and set racks in upper and lower thirds of oven. Line two baking sheets with parchment paper.

Step 3

In a small bowl, make an egg wash by mixing the remaining egg yolk with 1 teaspoon water. Set aside.

Step 4

Remove the dough from the refrigerator and place on a lightly floured work surface. Working with one disc of dough at a time, roll to 1/8-inch thick, turning and dusting with more flour as necessary so it doesn't stick. Using a cookie cutter or glass, cut out 3-inch circles and place about 1/2-inch apart on the prepared baking sheets. Re-roll and re-cut any excess dough. Brush the dough very lightly with the egg wash. Place a level teaspoon of apricot jam on the center of each cookie (do not overfill). Fold in the sides, slightly overlapping the filling, to form a triangle so that each side of the cookie has a corner that folds over and a corner that folds under -- this creates a pattern that looks pretty (but don't fuss too much over it). Pinch the corners together neatly so that they form a point. Slide the pans into the refrigerator for 20 minutes to chill.

Step 5

Bake for 12-15 minutes, turning the pans halfway through baking, until the cookies are lightly golden on top and just starting to brown in the corners. Let the cookies cool on the baking sheet for a few minutes, then transfer to a wire rack to cool completely.

Step 6

Freezer-Friendly Instructions: The Dough can be Frozen for up to 3 Months: Shape the dough into 2 discs, wrap each securely in plastic wrap, and place them in a sealable bag. When ready to bake, remove the disks from the freezer, thaw the dough until pliable, and then proceed with recipe. To Freeze After Baking: Let the hamantaschen cool completely and store in an airtight container separating layers with parchment paper or aluminum foil. Before serving, remove the cookies from the container and let them come to room temperature.