Step 1

Preheat the oven to 180°C/350°F (160°C fan) with a shelf in the middle.

Step 2

Potatoes - Cut the potatoes into quarters, then sliced 4mm / 1/6" thick. Place cut potato in a large bowl of water (prevents from going brown, removes excess starch so it cooks quicker). Drain before use.

Step 3

Crunchy topping: Mix panko and olive oil in a bowl. Then stir in parmesan.

Step 4

Season fish: Sprinkle salt and pepper on both sides of the fish fillets. Set aside.

Step 5

Sauté - Melt butter in a large oven-proof skillet (30cm/12") over high heat until foamy. Add leek and garlic, then cook for 3 minutes.

Step 6

Sauté potatoes - Add potato, salt and pepper. Cook for 6 minutes, stirring regularly. The potatoes should be half cooked at this stage.

Step 7

Reduce wine and stock - Pour in white wine. Simmer rapidly until it is mostly evaporated - about 1 minute. Pour in stock, then simmer for 1 1/2 minutes or until reduced by half.

Step 8

Top with fish - Turn the stove off. Place fish on top of the potatoes, presentation side up. (Note Pour cream all over, aiming for full coverage. Sprinkle with panko breadcrumbs.

Step 9

Bake for 30 minutes - I know this sounds like a long time but the fish stays succulent!

Step 10

Colour topping - Switch to the oven grill (broiler) on high and move the skillet up to the top shelf. Grill/broil 4 minutes or until golden.

Step 11

Rest - Remove and rest for 5 minutes, then serve! Eat the fish and gratin together with each mouthful for maximum eating pleasure!!