Preheat oven to 400°F. Line a large baking sheet with parchment.
Unfold puff pastry on a lightly floured surface. Gently roll to even thickness.
Cut each sheet into 4 rectangles to make 8 pieces total.
Place a line of chocolate near one short edge of each rectangle.
Roll up tightly into a log, seam-side down. Tuck ends slightly to seal.
Brush tops with milk and sprinkle with coarse sugar if using.
Bake 18–22 minutes until puffed and deeply golden.
Cool 5 minutes on the pan. Serve warm or at room temperature.