Step 1

Whisk together the hoisin sauce, ketchup, soy sauce, vinegar, sesame oil, garlic and ginger in a large bowl. Add the cod and turn to coat. Cover and refrigerate 1 hour.

Step 2

Remove the fish from the refrigerator. Position a rack in the middle of the oven and preheat the broiler. Line a baking sheet with foil. Remove the fish from the marinade, reserving the marinade, and arrange on the pan (if the fillets are skin-on, arrange them skin-side down).

Step 3

Broil the fish 4 minutes. Brush with the reserved marinade, making sure to coat the top and sides. Rotate the pan 180 degrees and broil until the fish is charred in spots and flakes easily with a fork, 4 to 5 more minutes.

Step 4

Arrange the fillets on a platter. Sprinkle with sesame seeds and sliced scallions.