Beat the butter, cream cheese, and salt on medium-high speed for about 2 minutes until fluffy and smooth. Scrape the bowl and add the flour, beating on low speed for about 30 seconds until the flour is blended in. Place the dough on a piece of plastic wrap, shaping it into an 8" x 4" rectangle. Wrap the plastic around the dough and chill it for 1 hour. Preheat a conventional oven to 350 °F or a convection oven to 325°F, and arrange the racks so they divide the oven in thirds. Line two baking sheets with parchment. Remove the dough from the refrigerator and divide it into 4 equal pieces. Work with one piece at a time, refrigerating the remaining dough until you use it. Roll a piece of the dough out on a floured surface, into a 5" x 15" rectangle. Spread 1/3 C of the apricot jam evenly over the dough. Starting at the long end of the dough, roll the dough into a log. Trim about 1/2" off each end, and then cut the log into 18 equal pieces. Place the pieces seam-side down onto the lined baking sheets, about 1/2" apart. Repeat with the remaining dough. When all of the dough has been used, brush the tops with the egg yolk mixture and sprinkle with the sugar. Bake in the preheated oven for about 18 to 20 minutes, rotating the pans halfway through the baking time. The Rogelach is done when it is golden brown. Remove the pans from the oven and place them on wire racks to cool. When the Rogelach is completely cool, store it in an airtight container, with wax paper between the layers, for up to a week. 6 dozen.
Chef's Note: Rogelach is so delicious and versatile, but also it is made with a dough that is very easy to work with. If you mess this dough up when you roll it, just re-roll it--no problem. You can also fill it with any type of jam that you prefer, and you can sprinkle the jam with nuts or chocolate chips before you roll up the dough. Recipe submitted by E. Talanian, author of Chewy Cookies.