For the dough: Pulse the flour, sugar and salt in a food processor until combined. Add the butter and pulse until it resembles coarse sand with some pea-sized pieces of butter, about 20 pulses. Add the cream cheese and sour cream, and pulse until it comes together in a rough dough; (with some uneven pebbles sized-pieces). Turn the dough out onto a floured work surface and divide into four equal portions. Pat each portion into a flat square and wrap in plastic wrap. Freeze for 15 minutes.
Foe the filling: Meanwhile, chop the hazelnuts in a clean food processor. Add the preserves, raisins and salt; and puree to make a very smooth paste.
Roll a portion of dough into a 6- by 14-inch rectangle about 1/4-inch thick. (Don't worry about slightly rough edges; these will be rolled inside of the rugalach.) Spread one-quarter of the filling over the surface with a small spatula. Starting with a long side, roll the dough up into a tight cylinder; ending with the seam on the bottom. Press the top slightly to flatten and wrap in plastic wrap. Freeze for another 15 minutes. Repeat with the remaining dough and filling. (The cylinders can be frozen for up to a month.)
Meanwhile, preheat the oven 375 degrees F and evenly position the racks. Line two baking sheets with parchment paper or silicone baking mats.
Slice the cylinders into 1 1/2-inch pieces, and place seam-side down on the prepared sheets. Whisk the egg yolks together and brush over the tops. Sprinkle with sugar and bake until pale golden and crispy on top, about 25 minutes.
Remove from the oven and let cool slightly on the baking sheets. Carefully transfer the rugelach to a rack to cool. Store in a tightly sealed container for up to 3 days.
From Food Network Kitchens