📝 About This Recipe
Born in the 1940s in a famous Porto eatery, this iconic dish is a masterclass in Portuguese comfort, featuring succulent salt cod loins poached in aromatic milk. The fish is nestled on a bed of caramelized onions, blanketed in a rich, velvety mayonnaise crust, and ringed by peaks of buttery mashed potatoes. It is a harmonious marriage of salty, sweet, and creamy textures that transforms humble ingredients into a celebratory centerpiece.
🥗 Ingredients
The Star Component
- 800 grams Salted Cod (Bacalhau) (high-quality thick loins, soaked for 48 hours with frequent water changes)
- 750 ml Whole Milk (to poach the cod)
- 2 Bay Leaf (fresh or dried)
- 5 whole Black Peppercorns
The Onion Bed (Cebolada)
- 3 large Onions (thinly sliced into half-moons)
- 100 ml Extra Virgin Olive Oil (high quality Portuguese oil preferred)
- 4 cloves Garlic (thinly sliced)
- 50 ml White Wine (dry variety)
The Duchess Potatoes
- 1 kg Starchy Potatoes (peeled and cubed (Russet or Yukon Gold))
- 50 grams Unsalted Butter (at room temperature)
- 2 large Egg Yolks (to enrich the mash and help it brown)
- 1/4 teaspoon Nutmeg (freshly grated)
The Topping and Garnish
- 1.5 cups Mayonnaise (high-quality store-bought or homemade)
- 12 whole Black Olives (traditional Portuguese small olives)
- 1 handful Fresh Parsley (finely chopped)
- 1/2 Red Bell Pepper (roasted and sliced into strips for decoration)
👨🍳 Instructions
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1
Begin by poaching the cod. Place the soaked cod loins in a deep saucepan and cover with the milk, bay leaves, and peppercorns. Bring to a very gentle simmer over medium-low heat for 10-12 minutes. Do not boil vigorously, or the fish will become tough.
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2
While the fish poaches, boil the potatoes in salted water until tender, about 15-20 minutes. Drain them well and let them steam dry for a minute to ensure a fluffy mash.
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3
Mash the potatoes until perfectly smooth. Incorporate the butter, egg yolks, and nutmeg. If the mash is too stiff, add 2-3 tablespoons of the warm poaching milk. Season with salt and pepper to taste. Set aside.
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4
Remove the cod from the milk using a slotted spoon. Carefully remove any remaining skin or bones, keeping the loins as whole as possible. Reserve a small amount of the poaching milk.
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5
In a large skillet, heat the olive oil over medium heat. Add the sliced onions and cook slowly for 15 minutes until they are soft, translucent, and just beginning to golden. Add the garlic in the last 5 minutes.
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6
Deglaze the onion mixture with the white wine, allowing the alcohol to evaporate. Add 2 tablespoons of the cod-poaching milk to the onions to create a silky base. Season lightly.
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7
Preheat your oven to 200°C (400°F). Select a beautiful ceramic baking dish for assembly.
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8
Spread the caramelized onion mixture (the 'cebolada') evenly across the bottom of the baking dish.
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9
Place the cod loins on top of the onion bed. They should be the centerpiece of the dish.
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10
Using a piping bag with a star tip (or a spoon for a rustic look), create a decorative border of mashed potatoes around the edges of the dish, encircling the cod.
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11
Generously spread the mayonnaise over the top of the cod loins, ensuring they are completely covered. This acts as a sealant to keep the fish moist.
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12
Bake in the preheated oven for 15-20 minutes, or until the potato peaks are golden brown and the mayonnaise has formed a beautiful, bubbling, toasted crust.
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13
Remove from the oven and garnish immediately with black olives, strips of roasted red pepper, and a sprinkle of fresh parsley.
💡 Chef's Tips
Always use thick-cut cod loins (lomos) for this recipe as they retain moisture better under the high heat of the oven. If your mayonnaise is very thick, whisk in a teaspoon of lemon juice to lighten it before spreading; this adds a brightness that cuts through the richness. For the smoothest potatoes, use a ricer or food mill rather than a masher. Be careful with salt! The cod, even after soaking, and the mayonnaise both contain salt, so taste your onions and potatoes before adding more. If the top isn't browning enough, turn on the broiler for the final 2 minutes, but watch it closely to prevent the mayonnaise from breaking.
🍽️ Serving Suggestions
Pair with a crisp, chilled Vinho Verde to balance the richness of the mayonnaise and butter. A simple side of blanched green beans or a fresh green salad with a sharp vinaigrette provides a nice textural contrast. Serve directly from the baking dish at the table to showcase the beautiful potato piping and golden crust. Fresh crusty sourdough bread is essential for mopping up the delicious olive oil and onion juices at the bottom of the dish.