Homemade Fish Gratin with Mashed Cod
Homemade Fish Gratin with Mashed Cod is the ultimate comfort dish for seafood lovers. Creamy, savory, and baked until golden, this gratin combines tender cod, fluffy mashed potatoes, and a rich white sauce for a hearty, satisfying meal. It’s perfect for weeknight dinners, family gatherings, or when you want something warm and nourishing straight from the oven.
Simple ingredients and classic flavors make this dish a timeless favorite, especially in coastal and European home cooking.
Why You’ll Love This Recipe
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Comfort food classic: Creamy, filling, and cozy
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Family-friendly: Mild flavors everyone enjoys
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Budget-friendly: Uses simple, affordable ingredients
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Make-ahead option: Great for busy days
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Freezer-friendly: Ideal for meal prep
Ingredients (Serves 4–6)
For the Mashed Cod
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1½ lb (700 g) cod fillets (fresh or frozen)
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1½ lb (700 g) potatoes, peeled and cubed
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3 tbsp butter
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½ cup milk (warm)
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Salt and black pepper, to taste
For the Cream Sauce
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2 tbsp butter
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2 tbsp all-purpose flour
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1½ cups milk
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½ tsp salt
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¼ tsp white or black pepper
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Pinch of nutmeg (optional)
For the Gratin
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1 small onion, finely chopped
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1 tbsp olive oil
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1 cup grated cheese (cheddar, Gruyère, or mozzarella)
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2 tbsp breadcrumbs (optional, for topping)
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Fresh parsley, chopped (optional)
Instructions
Step 1: Cook the Cod
Bring a pot of lightly salted water to a gentle simmer. Add the cod fillets and cook for 6–8 minutes, until opaque and flaky. Drain well and gently flake the fish, removing any bones. Set aside.
Step 2: Make the Mashed Potatoes
Boil the potatoes in salted water until tender, about 15–20 minutes. Drain and mash with butter, warm milk, salt, and pepper until smooth. Fold in the flaked cod gently. Set aside.
Step 3: Prepare the Cream Sauce
In a saucepan, melt butter over medium heat. Stir in the flour and cook for 1 minute. Gradually whisk in the milk until smooth. Simmer until thickened, about 3–5 minutes. Season with salt, pepper, and nutmeg if using.
Step 4: Sauté the Onion
Heat olive oil in a skillet and sauté the chopped onion until soft and translucent, about 5 minutes. Add to the cream sauce.
Step 5: Assemble the Gratin
Preheat oven to 375°F (190°C). Grease a baking dish.
Spread the mashed cod mixture evenly in the dish. Pour the cream sauce over the top. Sprinkle with grated cheese and breadcrumbs if using.
Step 6: Bake
Bake uncovered for 30–35 minutes, or until the top is golden and bubbling.
Step 7: Serve
Let the gratin rest for 5–10 minutes before serving. Garnish with fresh parsley if desired.
Tips for the Best Fish Gratin
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Drain cod well: Prevents excess moisture
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Use starchy potatoes: Like Russet or Yukon Gold
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Don’t overmix: Keeps the mash light
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Cheese choice matters: Gruyère adds depth, cheddar adds sharpness
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Golden top: Broil briefly if needed
Variations
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Add Vegetables: Peas, spinach, or leeks work beautifully
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Lighter Version: Use low-fat milk and reduce cheese
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Garlic Lover’s Version: Add minced garlic to the sauce
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Herb-Infused: Add dill, thyme, or chives
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Seafood Mix: Combine cod with shrimp or salmon
Serving Suggestions
Serve fish gratin with:
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Steamed green beans or broccoli
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Fresh garden salad
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Crusty bread or dinner rolls
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Lemon wedges for brightness
Storage & Reheating
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Refrigerator: Store covered for up to 3 days
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Freezer: Freeze before or after baking for up to 2 months
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Reheat: Oven at 350°F (175°C) until warmed through
Why This Recipe Works
The mild flavor of cod pairs perfectly with creamy mashed potatoes and a velvety white sauce. Baking the dish allows the flavors to meld while creating a golden, slightly crisp topping. This balance of textures—soft, creamy, and lightly crunchy—makes fish gratin a comforting and satisfying meal.
Final Thoughts
Homemade Fish Gratin with Mashed Cod is a timeless dish that brings warmth and comfort to the table. Easy to prepare and endlessly adaptable, it’s a perfect choice for family dinners or make-ahead meals.
Once you try it, this comforting gratin is sure to become a regular favorite in your kitchen.