Portuguese Cod Fish Casserole, known as Bacalhau com Natas in Portugal, is a beloved comfort food that combines flaky salt cod with creamy potatoes, caramelized onions, and a rich béchamel sauce. This dish is a staple in Portuguese cuisine and represents the country’s deep connection to the sea and its centuries-old tradition of preserving cod. Layers of tender potato slices, savory cod pieces, and sweet onions are bathed in a luscious cream sauce, then baked until golden and bubbling. The top becomes beautifully browned and slightly crispy while the inside stays creamy and comforting. Despite its elegant appearance and complex flavors, this casserole is surprisingly straightforward to make at home. It’s perfect for Sunday family dinners, special occasions, or any time you want to serve something that feels both homey and impressive.
Serving Quantity: 6 servings
Cooking Time: 1 hour 30 minutes (plus overnight soaking time for the cod)
1. Ingredients
- 1 and 1/2 pounds salt cod (bacalhau)
- 2 pounds potatoes, peeled and sliced thin
- 2 large onions, thinly sliced
- 4 cloves garlic, minced
- 3 cups heavy cream
- 1 cup whole milk
- 3 tablespoons butter
- 3 tablespoons all-purpose flour
- 1/4 cup olive oil
- 1 cup shredded mozzarella or Portuguese cheese
- 1/2 teaspoon nutmeg
- 1/2 teaspoon black pepper
- 1/4 teaspoon white pepper
- Salt to taste
- 2 bay leaves
- Fresh parsley for garnish
- Black olives for garnish (optional)
- Cooking spray
2. Nutrition Information Per Serving
- Calories: 620
- Protein: 38g
- Carbohydrates: 38g
- Fat: 36g
- Fiber: 3g
- Sodium: 1450mg
3. Soak the Salt Cod
This step must be done 24 to 48 hours before you plan to cook. Place the salt cod in a large bowl and cover it completely with cold water. Refrigerate and change the water every 6 to 8 hours, at least four times total. This removes the excess salt that was used to preserve the fish. After the final soak, the cod should taste mildly salty like ocean water, not intensely salty. If you taste a small piece and it’s still very salty, soak it a few more hours with fresh water.
4. Cook the Salt Cod
Drain the soaked cod and place it in a large pot. Cover with fresh cold water and add the bay leaves. Bring to a gentle simmer over medium heat, but don’t let it boil vigorously or the fish will become tough. Simmer gently for about 10 to 15 minutes until the fish is cooked through and flakes easily. The exact time depends on the thickness of your pieces. Remove the cod from the water and let it cool on a plate.
5. Prepare the Cod
Once the cod is cool enough to handle, remove and discard the skin and any bones. Use your fingers to flake the cod into bite-sized pieces, breaking it along its natural grain. Don’t shred it too finely, you want chunky flakes that will hold their shape in the casserole. Set the flaked cod aside in a bowl.
6. Slice the Potatoes
Peel the potatoes and slice them into rounds about one-eighth inch thick. Try to keep them uniform so they cook evenly. You can use a mandoline slicer for perfectly even slices, but a sharp knife works fine too. Place the sliced potatoes in a bowl of cold water to prevent them from browning while you prepare the other ingredients.
7. Caramelize the Onions
Heat 2 tablespoons of olive oil in a large skillet over medium heat. Add the thinly sliced onions and a pinch of salt. Cook slowly, stirring occasionally, for about 15 to 20 minutes until the onions are soft, golden, and sweet. They should be caramelized and almost melting. This step is important because it adds wonderful depth and sweetness to the casserole. Add the minced garlic in the last 2 minutes of cooking. Remove from heat and set aside.
8. Par-Cook the Potatoes
Drain the potato slices and pat them dry with a clean kitchen towel. Heat the remaining 2 tablespoons of olive oil in a large pan over medium heat. Working in batches, cook the potato slices for about 3 to 4 minutes per side until they’re lightly golden and about halfway cooked. They should be tender but still hold their shape. Don’t cook them completely or they’ll fall apart in the casserole. Transfer the cooked potato slices to a plate.
9. Make the Cream Sauce
In a medium saucepan, melt the butter over medium heat. Once it’s foaming, add the flour and whisk constantly for about 2 minutes to create a roux. It should smell slightly nutty but not brown. Gradually pour in the milk while whisking constantly to prevent lumps. Once the milk is incorporated, slowly add 2 cups of the heavy cream, whisking continuously. Keep whisking until the sauce thickens and coats the back of a spoon, about 5 to 7 minutes.
10. Season the Sauce
Add the nutmeg, black pepper, and white pepper to the cream sauce. Stir well to combine. Taste the sauce and add a small amount of salt if needed, but remember the cod and cheese will add saltiness. The sauce should be thick, creamy, and well-seasoned. Remove from heat.
11. Prepare the Baking Dish
Preheat your oven to 375 degrees Fahrenheit. Spray a 9 by 13 inch baking dish or a similar sized casserole dish generously with cooking spray. This prevents sticking and makes serving easier.
12. Assemble the First Layer
Arrange half of the par-cooked potato slices in an overlapping layer on the bottom of the prepared baking dish. They should cover the entire bottom with slight overlap. Season lightly with a tiny pinch of salt and pepper.
13. Add the Cod and Onions
Spread all of the flaked cod evenly over the potato layer. Top the cod with all of the caramelized onions and garlic, distributing them evenly. The onions add moisture and flavor throughout the casserole.
14. Add the Second Potato Layer
Arrange the remaining potato slices over the onions and cod in another overlapping layer. Try to create an attractive pattern since this will be visible on top. The potatoes should completely cover the filling.
15. Pour the Cream Sauce
Pour the prepared cream sauce evenly over the top layer of potatoes, making sure it seeps down into all the layers. Use a spoon to help distribute it if needed. Pour the remaining 1 cup of heavy cream over the entire casserole. The liquid should come almost to the top of the potatoes but not completely cover them.
16. Add the Cheese
Sprinkle the shredded mozzarella or Portuguese cheese evenly over the top of the casserole. This will create a golden, bubbly, delicious crust as it bakes.
17. Bake the Casserole
Place the casserole on the middle rack of the preheated oven. Bake uncovered for 45 to 50 minutes until the top is golden brown and bubbling, and the potatoes are completely tender when pierced with a knife. If the top is browning too quickly, tent it loosely with aluminum foil for the last 10 to 15 minutes.
18. Rest and Serve
Remove the casserole from the oven and let it rest for 10 to 15 minutes before serving. This allows the layers to set and makes it much easier to cut clean portions. The casserole will be extremely hot, so this resting time also prevents burned mouths.
19. Garnish and Enjoy
Garnish the casserole with freshly chopped parsley and black olives if desired. The olives are traditional in Portugal and add a nice briny contrast to the rich, creamy casserole. Cut into squares and serve hot with a simple green salad and crusty bread.
20. Tips for Success
Finding salt cod can be the biggest challenge. Look for it in the international section of larger supermarkets, Portuguese or Spanish markets, or Italian delis. It usually comes in wooden boxes or vacuum-sealed packages. Don’t skip the soaking process or your casserole will be inedibly salty. The water needs to be changed multiple times to properly desalinate the fish. If you’re short on time, you can use fresh cod instead, but the flavor won’t be quite as authentic. Season it generously with salt before cooking. Portuguese cheese like Queijo da Serra or Queijo São Jorge is traditional, but mozzarella, Gruyère, or even cheddar work well as substitutes. Each creates a slightly different flavor profile. The key to success is not rushing the caramelization of the onions. Slow cooking brings out their natural sweetness and creates depth of flavor that’s essential to this dish. Par-cooking the potatoes before assembling is important. Raw potatoes won’t cook through during the baking time, and fully cooked potatoes will fall apart. You want them about halfway done. Some versions include chopped hard-boiled eggs layered in with the cod. This adds protein and a traditional Portuguese touch. Add 3 to 4 peeled and sliced hard-boiled eggs if you like. This casserole can be assembled several hours ahead or even the day before. Cover tightly with plastic wrap and refrigerate, then bake when ready. Add 10 to 15 extra minutes to the baking time if starting from cold. Leftovers keep well for up to three days in the refrigerator and reheat beautifully. Cover with foil and warm in a moderate oven until heated through. For a lighter version, you can use half-and-half instead of heavy cream, though the texture will be less rich and luxurious. A food processor with a slicing blade makes quick work of slicing the potatoes uniformly and saves lots of time. This dish is quite rich, so serve it with light, acidic sides like a tomato and onion salad dressed with vinegar, steamed green beans, or a crisp lettuce salad. In Portugal, this casserole is often served on special occasions and holidays. It’s comfort food that also feels celebratory and special enough for company.
