Fish and Seafood Gratin

Ingredients

• 500 g Halibut (or other boneless white fish) (cut into large pieces)
• 300 g Frozen seafood mix (squid, shrimp, mussels) (quickly thawed under cold water)
• 2 c. à soupe Olive oil
• 2 gousses Garlic (finely chopped)
• 1 petite Shallot (finely chopped)
• 30 g Butter
• 30 g All-purpose flour (about 2 tbsp)
• 250 ml Whole milk (or fish stock for more flavor)
• ½ c. à café Salt
• ½ c. à café Black pepper
• ½ c. à café Garlic powder
• a pinch Nutmeg (optional)
• 150 g Grated mozzarella
• 1 c. à soupe Fresh parsley or Herbes de Provence (chopped)

Instructions

1. Prepare the ingredients

   Cut the halibut into large pieces, finely chop the garlic and shallot. Lightly season the fish with salt and pepper.

   Time: PT5M

2. Heat the oil

   Pour 2 tbsp olive oil into the pan and heat over medium‑high heat until it shimmers.

   Time: PT2M

3. Sear the fish

   Place the halibut pieces in the pan, let them brown 2‑3 minutes each side, then remove and set aside.

   Time: PT5M

4. Cook the seafood

   In the same pan, add the frozen seafood mix and sauté over high heat 4‑5 minutes until nicely colored.

   Time: PT5M

5. Add aromatics

   Stir in the chopped garlic and shallot, sauté for 2 minutes while stirring constantly.

   Time: PT2M

6. Prepare the béchamel

   Melt the butter in a saucepan over medium heat, add the flour and whisk for 1 minute until a pale roux forms.

   Time: PT2M

7. Thicken the sauce

   Gradually pour the milk (or fish stock) while whisking, season with salt, pepper, garlic powder and nutmeg. Cook 6‑7 minutes, stirring, until thickened.

   Time: PT7M

8. Preheat the oven

   Turn on the oven and preheat to 180°C.

   Time: PT5M

   Temperature: 180°C

9. Assemble the gratin

   In an oven‑proof dish, spread a thin layer of béchamel, arrange the fish pieces, distribute the seafood, pour the remaining béchamel, sprinkle with grated mozzarella and chopped parsley.

   Time: PT5M

10. Bake

    Bake the gratin for 20 minutes until the cheese is golden and bubbling.

    Time: PT20M

    Temperature: 180°C

11. Rest and serve

    Remove the dish from the oven, let rest 5 minutes before serving.

    Time: PT5M

Nutrition Facts

Calories

460

Protein

40 g

Carbohydrates

20 g

Fat

18 g

Fiber

0 g

Ingredient Substitutions

• Instead of Halibut (or other boneless white fish): Cod, Sea bass
• Instead of Frozen seafood mix (squid, shrimp, mussels): Fresh seafood, Shrimp only
• Instead of Olive oil: Sunflower oil, Butter
• Instead of Garlic: Garlic powder
• Instead of Shallot: Sweet onion
• Instead of Butter: Margarine
• Instead of All-purpose flour: Rice flour (for gluten‑free version)
• Instead of Whole milk: Reduced‑fat milk, Fish stock
• Instead of Garlic powder: Fresh garlic
• Instead of Grated mozzarella: Gruyère, Emmental
• Instead of Fresh parsley or Herbes de Provence: Basil, Chives

Equipment Needed

• Large skillet
• Saucepan
• Whisk
• Oven‑proof dish
• Oven
• Chef's knife
• Cutting board
• Silicone spatula (optional)
• Measuring tools (spoons and measuring cup) (optional)

Critical Steps — Do Not Skip

• Do not overcook the halibut during the initial sear.
• Achieve a smooth béchamel without lumps.
• Bake until the cheese is golden.

Chef Tips from the Video

• Use fish stock instead of milk for a stronger sea flavor.
• Add a pinch of sweet paprika to the béchamel for a slight color and smoky taste.
• Drizzle a little extra‑virgin olive oil over the top before baking for an even more golden crust.

Troubleshooting

Storage

Refrigerator: Store the gratin in an airtight container for 2‑3 days in the refrigerator.

Freezer: Can be frozen uncooked, with béchamel and cheese packaged separately, for up to 1 month.

Room temperature: Do not leave at room temperature for more than 2 hours.

Make-Ahead Tips

• Prepare the béchamel ahead of time and gently reheat before assembling.
• Assemble the gratin, cover and refrigerate up to 24 h before baking.
• Bake the gratin ahead of time, let cool, then reheat in the oven at 180 °C for 10‑12 min.