2 sticks (1 cup) unsalted butter, room temperature
8 ounces cream cheese, room temperature
¾ cup granulated sugar
¼ teaspoon plus a pinch of salt
1 large whole egg, plus 3 large egg yolks
2-1/3 cups all-purpose flour, plus more for dusting
1 teaspoon pure vanilla extract
1¼ cups (4 ounces) walnut halves or pieces
Pinch of ground cinnamon
1 cup plus 2 tablespoons (12 ounces) apricot jelly, melted
2 cups currants, raisins or other dried fruit, or mini chocolate chips
Fine sanding sugar (or granulated sugar), for sprinkling
1. In the bowl of an electric mixer fitted with the paddle attachment, beat the butter and cream cheese on medium speed until light and fluffy, 3 to 4 minutes, scraping down the sides of the bowl. Add ½ cup granulated sugar and ¼ teaspoon salt; beat until combined and fluffy, about 3 minutes. Add the egg yolks, one at a time, beating to combine after each. With the mixer on low speed, beat in flour to combine. Mix in vanilla.
2. Turn out the dough onto a lightly floured work surface. Divide into three equal pieces, and shape into flattened disks; wrap each in plastic. Refrigerate at least 1 hour or overnight.
3. Preheat the oven to 325°F, with racks in the upper and lower thirds. Line three baking sheets with parchment paper; set aside. In food processor, pulse together the walnuts, remaining ¼ cup granulated sugar, the cinnamon, and pinch of salt until finely ground; set aside. On a lightly floured work surface, roll out one disk of dough into a 10-inch round about ¼ inch thick. Brush the top evenly with melted jelly. Sprinkle with a third of the walnut mixture and a third of the currants. Using the rolling pin, gently roll over the round to press the filling into the dough.
4. Using a pizza cutter or sharp knife, cut the round into 16 equal wedges. Beginning with the outside edge of each wedge, roll up to enclose filling. Place about 1 inch apart on the prepared baking sheets. Repeat with remaining dough and filling ingredients. Lightly beat the whole egg; brush over tops, and sprinkle with sanding sugar.
5. Bake two sheets, rotating halfway through, until the cookies are golden brown, 20 to 25 minutes. Transfer to a wire rack to cool completely. Repeat with remaining baking sheet. Rugelach can be kept in an airtight container at room temperature for up to 4 days.