Steamed Seafood Dumplings

FOR THE DUMPLINGS:
Process the cod and egg in a food processor to a smooth puree. Add the shrimp and pulse on and off so the shrimp are coarsely chopped with the fish. Transfer the fish mixture to a medium bowl and mix in the ginger, water chestnuts, and scallions. Season the dumpling filling with the coriander, soy sauce and pepper.

Dust a baking sheet with cornstarch or line it with parchment. Place 2/3 tablespoon of the dumpling filling on the upper half of a won ton wrapper. Fold the skin over the filling and pinch together at the center of the edge. Make 3 small pleats in the side of the skin facing you, to the right side of the center point, and then 3 more on the left side, to seal the dumpling. Press the dumpling skin edges firmly together to seal. Place the dumplings on the prepared sheet pan. Repeat with the remaining filling and won ton wrappers. The dumplings are ready to be steamed, or they can be refrigerated up to 24 hours before steaming.

FOR THE SAUCE:
Mix all the sauce ingredients together in a small bowl.

Line a steamer basket with the cabbage leaves. Set the dumplings in the steamer basket, about 1/2-inch apart. Steam the dumplings in batches if necessary. (If you have a stacking-style steamer, you can steam multiple trays of dumplings at one time.) Place the steamer basket over a pan of boiling water and steam the dumplings for 5 to 7 minutes, or until the filling is completely cooked and the wrapper is tender. Transfer the dumplings to a serving plate with the dipping sauce and serve.