Preheat & Prep: Set your oven to 425°F and line a baking sheet with parchment paper.
Melt Butter: In a microwave-safe dish, melt butter in 20-second increments, stirring in between, or use a skillet over medium heat.
Prepare Panko Mixture: Chop 2 tablespoons of cilantro and stir it into the melted butter along with the panko and a generous pinch of salt.
Coat the Fish: Place the cod fillets on the prepared baking sheet, then coat them with olive oil, harissa, honey, and 1 teaspoon of salt. Use your hands to ensure even coverage, then firmly press the panko mixture onto the fish.
Bake: Roast the fish for 10–12 minutes, or until it flakes easily and the panko turns golden. If needed, broil for a couple of minutes for extra crispiness, keeping a close watch to prevent burning.
Make the Avocado Sauce: In a small bowl, mash the avocado with sour cream and ½ teaspoon of salt. Cut the lime in half and squeeze the juice from one half into the mixture, adjusting with more lime to taste.
Warm Tortillas: If using a gas stove, char the tortillas over an open flame for about 15–20 seconds per side. Alternatively, warm them in a dry skillet over medium-high heat.
Assemble Tacos: Use a fork to break the roasted fish into smaller pieces. Serve in warm tortillas, topping with cabbage, the remaining chopped cilantro, avocado-lime sauce, and extra harissa if desired.