For the filling: In a heatproof bowl, combine the tahini and chocolate. Melt in 40-second bursts at half power in a microwave, stirring until the mixture is smooth. Stir in the confectioners' sugar and vanilla. The mixture will be thick; if it's still runny, add another 1/4 cup confectioners' sugar., To assemble: Line a large baking sheet with parchment. Unwrap and roll the dough to a 12" x 18" rectangle. Trim 1/4" of dough from all around the rectangles edges (this will give you a higher puff in the oven)., Cut the dough in thirds in both directions, to make nine 4" x 6" rectangles., Roll the filling into a rope about 3/4" in diameter, cut in 4" lengths, and place one-third of the way up from the bottom of each rectangle., Fold the bottom up and over the filling, then fold over once more to get a packet with the filling snugged up against one edge and the seam on the bottom., With a bench knife, make three equidistant cuts through the edge where the filling is tucked in, two-thirds of the way through the packet. Transfer to the prepared baking sheet and curve the packet to spread out the "toes of the bear claw. Refrigerate the pastries for 30 minutes., After chilling, remove the bear claws from the refrigerator and let rise for 45 minutes to 1 hour at room temperature. They should expand noticeably, and when you gently press one with your finger, the indentation should remain., Partway through the rise time, preheat the oven to 425°F. When the pastries are not quite doubled, brush with the beaten egg and bake for 15 minutes., Reduce the oven temperature to 350°F and bake for 8 to 10 minutes more, until they're deep golden brown and you can smell the chocolate. Remove from the oven and let cool on the pan on a rack for 20 minutes before serving., Store loosely covered at room temperature for up to 2 days.