Butter two 13-by-9-inch baking pans. In a food processor, combine brown sugar, nuts, chocolate, cinnamon, and a pinch of salt. Pulse until coarsely ground; set nut mixture aside.
Divide dough in half. Working with one half at a time (keep the other half covered with plastic wrap), roll dough out to a 16-by-10-inch rectangle on a lightly floured work surface. Spread 4 tablespoons butter over dough, leaving a 1/2-inch border all around. Sprinkle half the nut mixture over butter. Leave a border around the filling so it doesn't seep,
Starting at a long end, roll up dough like a jellyroll; with a sharp knife, cut crosswise into 12 equal pieces.
Place buns, cut side down, in prepared pans. Cover pans loosely with plastic; let stand in a warm spot until doubled in size, about 1 1/4 hours.
Preheat oven to 375 degrees, with racks in upper and lower thirds. Bake buns until golden brown, 25 to 30 minutes, rotating pans back to front and top to bottom halfway through. Let cool 15 minutes.
Prepare glaze: In a small saucepan, heat brown sugar, butter, and water over medium, stirring, until simmering; cook 1 minute. Drizzle glaze over buns; let stand 10 minutes before serving.
The rolls can be shaped in advance and frozen for up to 2 months. No need to defrost -- just add 2 hours to the second rise.