Potato Cheese Halibut

This halibut gets a crust you won’t forget. Instant potato flakes mixed with grated Swiss cheese, Parmesan, mayonnaise, lemon juice, and horseradish create a thick, savory topping that bakes onto the fish and then broils golden brown. It’s like a potato gratin fused with a fish fillet in a single dish.

The two-stage cooking is what makes the crust work. Baking first at 400°F (204°C) cooks the fish through gently while the topping sets. Then a quick hit under the broiler crisps and browns the surface. You get a crunchy, golden top with moist, flaky fish underneath.

Horseradish in the topping adds a sharp, peppery bite that cuts through the richness of the mayonnaise and cheese. It’s only 1½ teaspoons, so it’s not overpowering. Just enough to remind you this isn’t a bland fish dinner.

Kitchen Tips

• Spread the topping evenly across each fillet. Thin spots burn under the broiler while thick spots stay pale.
• Use ¾-inch thick fillets as the recipe specifies. Thinner fillets overcook before the crust browns. Thicker fillets need longer baking time.
• Watch the broiler closely. The topping goes from golden to charred in under a minute. Stay by the oven during this step.
• Any firm white fish works. Cod, sea bass, or swordfish are solid substitutes if halibut isn’t available.

Variations

• Cheddar-dill version: Swap the Swiss for sharp cheddar and add 1 teaspoon dried dill to the topping for a different flavor profile.
• Panko crunch: Mix ¼ cup panko breadcrumbs into the potato flake mixture for an even crispier crust.