Heat the oven to 450F. Stir the sesame oil, stock, lemon zest, salt, ginger and 5-spice powder in a bowl. Place the parchment paper on a work surface. Divide the spinach amount the parchment squares (mound in the center). Top each with 1 piece fish. Spoon the stock mixture over the fish. Fold the parchment over to enclose the fish and fold the seams tightly to seal. Place the packets onto a baking sheet. Bake for 10 minutes or until the fish is done Open the packets carefully, the steam will be hot. Serve with sliced green onion and chopped cilantro sprinkled over the fish, if desired.