Baked Salt Cod and Golden Mashed Potato Gratin

Name: Baked Salt Cod and Golden Mashed Potato Gratin
Prep time: 60 min
Total time: 60 min
Yield: 8 servings
Cuisine: Française
Ingredients: 2 lb (1 kg) desalted salt cod flakes; 3 tablespoons extra-virgin olive oil; 3 garlic cloves, finely chopped; 3 onions, sliced into rings; 2 tomatoes, peeled, seeded and diced; ½ cup pitted black olives, roughly chopped; Fresh parsley and chives, to taste; Freshly ground black pepper, to taste; 1 lb (500 g) starchy potatoes (Russet or Maris Piper); 1 tablespoon unsalted butter; ¼ cup warm whole milk; Freshly grated nutmeg, to taste; Salt, to taste; 2 tablespoons butter (for topping); 1 small onion, finely chopped

By Marie Lefebvre · Updated October 31, 2026

Inspired by the beloved Brazilian escondidinho: tender salt cod flakes sautéed with garlic, tomatoes and olives, blanketed under a layer of buttery mashed potato and baked until beautifully golden. Pure comfort food, ready to share.

Prep⏱️ 60 min

Servings👥 8 servings

Difficulty📊 Medium

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🛒 Ingredients

8 servings

2 lb (1 kg) desalted salt cod flakes
3 tablespoons extra-virgin olive oil
3 garlic cloves, finely chopped
3 onions, sliced into rings
2 tomatoes, peeled, seeded and diced
½ cup pitted black olives, roughly chopped
Fresh parsley and chives, to taste
Freshly ground black pepper, to taste
1 lb (500 g) starchy potatoes (Russet or Maris Piper)
1 tablespoon unsalted butter
¼ cup warm whole milk
Freshly grated nutmeg, to taste
Salt, to taste
2 tablespoons butter (for topping)
1 small onion, finely chopped

🛍️ Recommended tools

🎂Moule à gâteauSee on Amazon →🪄Batteur électriqueSee on Amazon →⚖️Balance de cuisineSee on Amazon →

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Directions

1
At least 6 hours ahead: submerge the cod flakes in a large bowl with 4 quarts of cold water. Change the water at least once. Taste a small piece — if still too salty, soak again. Drain thoroughly and set aside.
2
Heat 1 tablespoon of olive oil in a large skillet over medium heat. Sauté the garlic and chopped onion for about 2 minutes until lightly golden and fragrant.
3
Add the diced tomatoes and cook 2 minutes, stirring occasionally. Add the drained cod flakes and cook gently for 1 minute — just enough to marry the flavours without drying the fish out.
4
Season carefully (the cod may still be slightly salty). Off the heat, gently fold in the olives and fresh herbs without breaking the flakes. Cover and set aside.
5
Peel the potatoes and cut into even chunks. Cover with cold salted water, bring to a boil and cook 10–12 minutes until fork-tender. Drain and mash immediately.
6
Stir in the butter then the warm milk until smooth. Season with salt, pepper and a grating of nutmeg. The mash should be slightly stiffer than usual so it holds its shape as a topping.
7
Preheat the oven to 400 °F (200 °C). Butter a baking dish and spread the cod mixture evenly over the bottom. Cover completely with the mashed potato, smoothing the surface with a spatula.
8
Dot the top with small knobs of butter and bake 20–25 minutes until the surface is golden and lightly crisp. Rest 5 minutes before serving straight from the dish.

💡 Chef's Tip

For an extra-indulgent finish, scatter 2 oz (50 g) of grated Gruyère or Parmesan over the mash before baking. Proper desalting is the make-or-break step — always taste the cod before cooking and adjust soaking time accordingly.