04Transfer dough to a lightly oiled large bowl and turn to coat with oil. Cover with a kitchen towel (not terry cloth) and let rise in a draft-free place at warm room temperature until doubled, about 2 hours.
05Butter 2 large baking sheets. Punch down dough, then roll out on a floured surface with a floured rolling pin into a 14-inch round (about 1/2 inch thick). Cut out as many rounds as possible with floured cutter, arranging 3 inches apart on baking sheets. Gather and reroll scraps once, then cut out more rounds.
06Loosely cover buns with oiled plastic wrap and let rise in a draft-free place at warm room temperature until they hold a finger mark when gently pressed, 1 1/2 to 2 hours.
07Preheat oven to 375°F with racks in upper and lower thirds.
08Brush buns with some of egg and sprinkle with sesame seeds. Bake, switching position of sheets halfway through, until tops are golden and undersides are golden-brown and sound hollow when tapped, 20 to 25 minutes. Transfer to racks to cool completely.
09Butter baking pans. Punch down dough, then divide into 16 equal pieces (about 3 oz each). Roll each piece of dough into a 6-inch-long log on a lightly floured surface. Space 8 logs evenly in each pan so that there are 2 columns of logs that run parallel to long sides of pan.
10Loosely cover buns with oiled plastic wrap and let rise in a draft-free place at warm room temperature until buns just start to touch, 1 1/2 to 2 hours.
11Preheat oven to 375°F with racks in upper and lower thirds.
12Bake buns, switching position of pans halfway through, until tops are golden and undersides are golden-brown and sound hollow when tapped, 20 to 25 minutes. Cool in pans 10 minutes, then transfer to racks to cool completely. Before using buns, pull apart and cut lengthwise down center of each (but not all the way through).