Prepare the Fish: Start by patting the cod fillets completely dry with a paper towel. This is a crucial step for getting a good sear. Season both sides lightly with a pinch of salt and black pepper.

Mix the Sauce: In a small bowl or jug, whisk together all the sauce ingredients: light soy sauce, dark soy sauce, honey, rice vinegar, toasted sesame oil, minced garlic, and grated ginger. Set it aside.

Heat the Pan: Place a large, non-stick frying pan or skillet over a medium-high heat. Add the vegetable oil and let it get hot – you should see it shimmer slightly.

Sear the Cod: Carefully place the cod fillets in the hot pan. Don't overcrowd it; cook in two batches if necessary. Sear the fillets for 3-4 minutes on the first side, undisturbed, until a golden-brown crust forms.

Flip and Add Sauce: Gently flip the fillets over using a fish slice or spatula. Immediately pour the prepared ginger soy sauce into the pan around the fish.

Glaze the Fish: The sauce will start to bubble and simmer right away. Reduce the heat to medium. Let it cook for another 4-5 minutes, spooning the simmering sauce over the tops of the fillets as it cooks. What works best for me is to tilt the pan slightly to pool the sauce, making it easier to spoon over.

Check for Doneness: The cod is cooked when it's opaque all the way through and flakes easily when gently prodded with a fork. The sauce should have thickened into a glossy glaze that coats the fish beautifully.

Serve Immediately: Remove the pan from the heat. Carefully transfer the glazed cod fillets to your plates. Spoon any remaining sauce from the pan over the fish. Garnish generously with the sliced spring onions, red chilli (if using), and a sprinkle of toasted sesame seeds before serving.