Preheat your oven to 200°C (fan-assisted) or 220°C conventional. Line a 9x13 inch baking dish with aluminium foil and lightly grease it. The oven should be fully hot before the fish goes in — you want that initial blast of heat to set the crust.

Pat the cod fillets dry with kitchen paper until they feel tacky rather than wet. Season both sides generously with salt and pepper. The fish should look matte and feel firm to the touch, with no visible glistening moisture.

Mix the wet ingredients in a small bowl: combine the melted butter, mayonnaise, Dijon mustard, lemon juice, and garlic powder. Stir until the mixture is smooth, pale yellow, and smells tangy and rich. It should have a thick, spoonable consistency.

Prepare the crust mixture in a separate shallow dish: stir together the panko breadcrumbs, grated parmesan, lemon zest, and paprika. The mixture should look golden and smell nutty and cheesy. Pinch some between your fingers — it should feel dry and crumbly, not clumpy.

Coat the fillets by brushing each one generously with the butter-mayonnaise mixture on all sides. Then press the coated fillet firmly into the breadcrumb mixture, turning to coat evenly. You should see a thick, even layer of crumbs adhering to the fish — the surface will look textured and speckled with green flecks of zest.

Arrange the coated fillets in the prepared baking dish, leaving at least 2cm of space between each one. If they're touching, the crust will steam rather than crisp. The fillets should sit flat and look like little golden pillows in the dish.

Bake for 18-20 minutes, or until the crust is deep golden brown and the fish flakes easily when tested with a fork. At the 15-minute mark, check the colour — the crust should be turning a rich amber. The kitchen will smell of toasted parmesan and warm butter. If the top is browning too quickly, tent loosely with foil for the final minutes.

Rest for 3 minutes after removing from the oven. The fish will continue cooking slightly, and the crust will set and become even crunchier. Garnish with fresh parsley and serve immediately with lemon wedges.