Method
Mix all the marinade ingredients except the sliced orange. Put the cod in a glass container, or non-metal dish/Tupperware, and add the marinade — gently rubbing to coat the fish.
Cover and refrigerate, ideally for 4+ hours or overnight. Take out of the fridge 20 minutes before roasting. If preparing it last minute, marinate at room temperature while the potato and fennel roasts.
Pre-heat oven to 200°C (fan) and line an oven tray/dish with baking parchment.
Peel, slice and rinse the potatoes, then place in the dish with ¼ tsp of sea salt, a pinch of black pepper, 2-3 tablespoons oil. Mix to coat the potatoes with the oil. Arrange in a single layer, or slightly overlapped, and roast for 20 minutes.
Meanwhile, in a small bowl mix the sliced onion, fennel, parsley, the remaining oil and a pinch of salt and pepper. Set aside a small handful of this mixture to cook with the fish later, and add the rest to the potatoes after 20 minutes. You can either mix them in if the potatoes don’t break or spread on top. Roast for 20 minutes more or until golden. If it starts to get too dark, you may want to cook the fish separately.
To cook the fish: either bake on top of the potatoes — skin down with the marinade and reserved fennel and onion on top for 12-15 minutes. Or, if you prefer the cod skin crisp, you can sear it first in a very hot pan, skin down for 2-3 minutes until the skin is crisp and the fish partially cooked, then gently place on top of the potatoes, skin up, with the marinade on top. Scatter the fresh orange slices over the potatoes and roast for 10 minutes. Serve hot.
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