Set the oven to 450°F with the rack in the middle position. Grab 4 large parchment sheets, and fold each in half. Draw half a heart on each sheet so that when you cut them out, you get full hearts. You know—like this:
Unfold the paper hearts and lay them flat. Place a cup of sliced bok choy on one side of each heart. Sprinkle salt and pepper on the bok choy.
Salt and pepper the chicken, too. Then, place a piece of chicken atop each pile of bok choy.
Top with ¼ of the mushrooms and shallots. Spoon 2 tablespoons of All-Purpose Stir-Fry Sauceonto each mound.
Fold the other half of each heart over the top. Tightly crimp the edges together, starting at the top-center of each heart. At the pointed bottom end, twist the paper to seal well. Repeat steps for the three remaining chicken packets.
Place the parchment packets on a rimmed baking sheet. Bake in the oven for 15 to 20 minutes or until the chicken is fully cooked. The breasts should register 150°F on an instant-read thermometer, and the thighs should register 165°F.
As soon as the packets are out of the oven, carefully cut them open. Serve immediately!
