Weigh your flour; or measure it by gently spooning it into a cup, then sweeping off any excess. Combine all of the dough ingredients. Allow the dough to rest for 20 minutes, covered., Knead the dough — by hand, mixer, or bread machine — until it's soft and somewhat sticky. Kneading by hand is tricky; avoid adding too much more flour (an oiled board and hands can help here)., Allow the dough to rise, covered, for about 90 minutes. It'll become puffy, but won't double in size. You'll find it loses most of its stickiness after this first rise., Gently deflate the dough, and divide it in half. On a lightly oiled surface, roll each half of the dough into an 8" x 9" rectangle., Cut each rectangle into six 4" x 3" pieces, for a total of 12 pieces. Keep the dough you're not working on covered., To shape: Turn one of the pieces of dough so the short (3") edge faces you. Put a stick of chocolate on the dough, about 1" from and parallel to the far edge., Fold the far edge toward you, over the stick, to the middle of the dough. Press the edge lightly to seal. Put a second stick on that sealed seam., Fold the near short edge away from you, over the second stick, and press lightly. This second seam should end up about 1" from the new top edge of the roll., Flip the shaped roll so that the seam side is down, and put it on a greased or parchment-lined baking sheet. Note: The pain au chocolat sticks won't melt out the end of the rolls as they bake, so there's no need to seal the outside edges of the dough., Repeat with each piece of dough, leaving about 1 1/2" between the finished rolls on the baking sheet., Cover the rolls and let them rise for 60 to 90 minutes, long enough to become puffy., About 15 minutes before the rolls are done rising, preheat your oven to 350°F., Brush each roll with a little milk., Bake the rolls for 14 to 18 minutes, until they're a light golden brown and register 190°F to 200°F on an instant-read thermometer inserted into the bread., Remove the rolls from the oven, and after 5 minutes transfer them to a rack. Dust with glazing sugar., Serve warm. The chocolate will harden as the rolls cool; if you want to serve rolls later, reheat them briefly (about 15 seconds in the microwave) just before serving, to melt the chocolate.