In a medium-sized mixing bowl, combine the soy sauce, honey, lime juice, grated ginger, minced garlic, sesame oil, and crushed red pepper flakes (if using). Whisk the ingredients together until they are well-blended, and set aside.

Season the cod fillets with salt and pepper on both sides. Place the fillets in a shallow dish, and pour the ginger-soy marinade over them. Ensure that the fillets are well-coated. Cover the dish with plastic wrap, and let the fish marinate in the refrigerator for 20-30 minutes.

After marinating, remove the cod fillets from the refrigerator, and let them sit at room temperature for 5-10 minutes. This allows for more even cooking.

In a large non-stick skillet, heat the vegetable oil over medium-high heat. Remove the cod fillets from the marinade, allowing any excess to drip off, and reserve the marinade for later use.

Carefully place the fillets in the hot skillet, and cook for 3-4 minutes on each side, or until the fish is opaque and flakes easily with a fork. Be sure not to overcrowd the pan; cook the fillets in batches if necessary.

While the fish is cooking, pour the reserved marinade into a small saucepan, and bring it to a boil. Cook for 2-3 minutes, allowing the sauce to thicken slightly.

To serve, place the cooked cod fillets on individual plates, and drizzle each fillet with the thickened ginger-soy sauce. Garnish with chopped cilantro, sliced green onions, and toasted sesame seeds.

Enjoy your savory cod fillets!