Preheat oven to 190 degrees C or 375 degrees F.
Layout parchment (waxed or baking) paper so that it is large enough to cover the fish and fold over a couple of times at the top and at the edges. Highly recommend that you double your paper. You can also use aluminum foil if you wish. Wash and pat dry cod fish. Remove any pin bones and remove skin. Place your fish in the middle of your laid out parchment paper add your trimmed green onions, julienned ginger, chili peppers, salt and white pepper and drizzle on 1 teaspoon of sesame oil for each fish. You should have 4 packets.
Fold up your cod parcels. Close the edges of the paper lengthwise centering your fish inside. Then fold the paper over twice while still leaving room for the fish. Then at each end fold each side twice while still leaving a little excess room for the fish. Crimp the edges with your fingers to make sure that each parcel stays together. (if you want you can add additional thin sliced veggies in the packet to cook at the same time)
Bake your cod parcels (depending on their size and weight between 8- 12 minutes. Set your timer at 6 minutes and check the packets by just unfolding carefully one end of the packet and if your fish flakes easily with a fork it is done. If not, close up and seal the packet and bake until your fish just starts to flake easily with your fork. My large 200 gram thick sliced fish took 12 minutes to cook and my smaller fish packets took between 7-8 minutes. Do not overcook!!! You can bake on a baking sheet or oven proof skillet. (I also chose to bake some vine ripe tomatoes with just a little olive oil and salt since I had the oven going and a great way to round out the meal) Keep the fish in the packets and serve right in the packets.
In the mean time while your fish is cooking make your black bean sauce on the stove top. In a small sauce pan, add your canola oil, ginger, scallions and garlic and saute just until aromatic. Add black bean paste, shoaxing wine, tamari (soy) sauce, sugar alternative if desired and water. Stir until well incorporated. If sauce is too thick, then add more water to thin out and if sauce is too thin just cook over low-medium heat until it is the consistency of applesauce.
Open up the fish packets and top with a drizzle of the black bean sauce and top with fresh garnishes like cilantro, green onions and chilis as desired. Enjoy!