Bacalhau com Natas — Cod and Potatoes Baked in a Creamy Sauce

Preheat a conventional oven (no fan) to 220°C and have ready a baking dish with a capacity of about 2.5 l. Cut the potatoes into cubes about 1.5 cm across, slice the onion into thin slivers and finely chop the garlic. Use desalted, refrigerated fillets that are ready to cook; the fish weight refers to drained flesh without skin or bones.

Toss the potatoes with 25 ml of olive oil and spread on a large baking sheet in a single layer. Roast for about 25–30 minutes, turning halfway through, until the edges are lightly golden and the cubes are almost tender when pierced with a fork. After taking out the potatoes, lower the oven temperature to 190°C. Prepare the fish, onion and sauce while the potatoes roast.

Bring 1000 ml of water to a gentle simmer in a wide pot, lower the heat and add the fillets. Cook with the lid ajar for about 8–10 minutes, keeping the liquid barely moving, until the flesh flakes easily; avoid vigorous bubbling, which breaks up the fish. Lift out the cod with a slotted spoon, drain and set aside for a few minutes until easy to handle. Discard the cooking water and separate the fish into large flakes, checking that no bones remain.

Heat the remaining 15 ml of olive oil in a large skillet over medium-low heat. Add the onion and bay leaf, then cook for about 10–12 minutes, stirring, until the onion softens and becomes translucent without deep browning. Add the garlic for the last minute, then remove the bay leaf and gently fold in the cod flakes. Warm over low heat for about 1–2 minutes, keeping the larger fish pieces intact.

Melt the butter in a saucepan over medium-low heat, add the flour and whisk for about 1–2 minutes until foamy but not brown. Gradually pour in the milk, whisking smooth after each addition, then simmer gently for about 5 minutes, stirring often. Pour in the cream, add the salt, pepper and nutmeg and heat for about 1–2 minutes more. The sauce should be smooth, creamy and fluid enough to coat the potatoes and fish freely.

In a large bowl, gently combine the roasted potatoes and the olive oil from the baking sheet, the cod with onion and about two-thirds of the cream sauce. Transfer to the baking dish and spread out without pressing down firmly. Pour the remaining sauce over the top and sprinkle evenly with the grated mozzarella.

Put the dish on the middle oven rack at 190°C. Bake for about 20–25 minutes, until the cheese melts and browns in places and the sauce bubbles gently around the edges. The potatoes should be fully tender and the center of the bake hot.

Take the dish out of the oven and let rest for about 10 minutes so the sauce thickens slightly. Divide into four portions, scooping up potatoes, fish flakes and creamy sauce from all the way down to the bottom of the dish. Serve hot.