Crispy Lemon Garlic Butter Cod and Potatoes Step-by-step instructions

Before you start

Before cooking, remove the cod from the refrigerator and let it sit at room temperature for no more than 30 minutes. Pat the fish dry with paper towels. Slice the potatoes into uniform 1/4-inch rounds.

Grate the Parmesan finely. Mince the garlic and chop the parsley. Halve the lemon. Measure the oil and butter. Have all ingredients within reach, as the cooking process moves quickly.

Instructions

Prep and Heat

1. 1Prep the Cod and Potatoes
   Slice the whole white cod loin crosswise into thick fillets, about 1 to 1 1/2 inches thick. Pat the fillets dry with paper towels. Slice the golden potatoes into 1/4-inch thick rounds. Grate the Parmigiano-Reggiano finely on a box grater. Season the fish and potatoes generously with kosher salt and black pepper.
   Look for The fish fillets are thick and even, the potato slices are uniform, and the cheese is finely grated.
   Tip Keep the potato slices thin so they cook through at the same rate as the fish.
2. 2Heat the Oil and Butter
   Place a large cast-iron or heavy skillet over medium-high heat. Add the neutral oil and 2 tablespoons of the butter. Swirl the pan as the butter melts and the oil shimmers. The pan is ready when the butter foams and the oil is hot but not smoking.
   Look for The butter is foamy and the oil shimmers, but the butter is not browning.
   Tip If the butter browns too quickly, lower the heat slightly.

The fish and potatoes are seasoned and ready. The pan is hot, and the butter is foaming but not browned. The oil shimmers, indicating it's ready for the fish. This phase sets the stage for a perfect sear.

Sear and Aromatics

3. 3Sear the Fish and Potatoes
   Carefully place the seasoned cod fillets and potato slices into the hot pan in a single layer, working in batches if needed. Do not overcrowd the pan. Sear without moving for 3 to 4 minutes, until a deep golden crust forms on the bottom. Flip the fish and potatoes with a fish spatula and cook for another 3 to 4 minutes, until the other side is golden and the fish is opaque and flakes easily.
   Look for The fish and potatoes have a crisp golden crust on both sides, and the fish flakes easily with a fork.
   Safe temperature 145°F (63°C) internal temperature (fish)
   Tip Resist the urge to move the fish too early; let the crust form before flipping.
4. 4Add Garlic and Remaining Butter
   Reduce the heat to medium-low. Add the remaining 1 tablespoon butter and the sliced garlic to the pan. Tilt the pan slightly and spoon the garlic butter over the fish and potatoes for about 1 minute, until the garlic is fragrant and the butter is sizzling. The fish should reach an internal temperature of 145°F (63°C).
   Look for The garlic smells fragrant and the butter is sizzling, coating the fish and potatoes.
   Safe temperature 145°F (63°C) internal temperature (fish)
   Tip Spooning the butter over the top adds flavor without overcooking the fish.

The fish and potatoes are golden and crisp on both sides. The garlic is fragrant and the butter is sizzling. The fish is opaque and flakes easily, and the internal temperature reaches 145°F (63°C).

Finish and Serve

5. 5Finish with Parmesan, Parsley, and Lemon
   Remove the pan from the heat. Scatter the freshly grated Parmesan cheese over the fish and potatoes. Sprinkle with the chopped parsley. Squeeze the fresh lemon juice over everything. Serve immediately while hot and crispy.
   Look for The cheese melts slightly over the hot fish, the parsley is bright green, and the lemon juice sizzles on contact.
   Tip For extra lemon flavor, add a few thin strips of lemon zest along with the juice.

The Parmesan is melted over the hot fish, the parsley is bright green, and the lemon juice adds a fresh, tangy finish. The dish is ready to serve immediately, with crispy edges and tender interiors.

Common mistakes

One common mistake is overcrowding the pan, which lowers the temperature and prevents browning. Another is moving the fish too early — let the crust form before flipping.

Overcooking the fish will make it dry; use a thermometer to ensure it reaches exactly 145°F (63°C).

Also, avoid using pre-shredded cheese, as it doesn't melt as smoothly and often contains anti-caking agents.

How to tell it’s done

The cod is done when it flakes easily with a fork and reaches an internal temperature of 145°F (63°C). The potatoes should be tender on the inside and crisp on the outside.

The crust should be deep golden brown, and the garlic butter should be fragrant. The Parmesan should be melted slightly, and the lemon juice should be bright and fresh.

• Fish: 145°F (63°C) in the thickest part
• Steaks, chops and roasts: 145°F (63°C) in the thickest part, then a 3-minute rest