Tip:Much of the excitement of cooking en papillote is the moment when you open the packets and release an enticing cloud of aromatic steam. So that everyone gets to experience that moment, serve the unopened packets on plates and let people open their own.
Position racks in the upper and lower thirds of the oven and heat the oven to 375°F.
Preprare the parchment packets. Cut four 15x24-inch sheets of parchment. Fold each sheet in half, forming a 15x12-inch rectangle. With a pencil, draw a half-heart on each, centering it on the folded edge. Cut out the hearts. (This shape is easier to seal than a rectangle.)
In a small bowl, stir the soy sauce, vinegar, hoisin sauce, lime juice, hot chili oil, and honey. In a medium bowl, combine the shrimp, ginger, and garlic. Pour about half of the soy mixture over the shrimp and toss to coat. In another medium bowl, combine the bok choy, scallions, and cilantro. Add the remaining soy mixture to the bowl and toss to coat.
Unfold the parchment sheets and arrange on a work surface. Brush the inside of each with oil, leaving a 3-inch border. Distribute the bok choy among the sheets, arranging it on one side. Pour over any liquid remaining in the bowl. Arrange the shrimp on the bok choy, using a rubber spatula to scrape any seasoning on top. Fold the other side of the parchment over the shrimp and line up the edges.
Starting at the top of the heart, fold over about 1/2 inch of the edge, pressing down to make a crisp crease.
Continue working your way around the edge of the packet, making overlapping folds (like pleats), always pressing firmly and creasing the edge so the folds hold. Twist the tip of the heart to finish. If necessary, make a second fold anyplace that doesn’t appear tightly sealed.
Transfer the packets to two large, rimmed baking sheets and bake for 8 minutes. Rotate and swap the baking sheets’ positions and continue to bake until the packets are puffed and fragrant, about 7 minutes more. Serve immediately.
Serve with soba noodles or steamed rice.