Creamy Baked Newfoundland Cod Au Gratin

If you grew up in Newfoundland, cod au gratin is one of those dishes that shows up at every potluck and Sunday supper for good reason. Tender, flaky cod baked in a rich, mustardy cheese sauce under a crunchy breadcrumb topping is pure comfort in a casserole dish.

It comes together in about 40 minutes with simple ingredients you probably already have, so it is an easy weeknight win that still feels a little special. The sauce is the real star here: creamy and sharp with just enough tang to cut through the richness.

What Makes This Cod Au Gratin So Good

The sauce is built on a simple butter-and-flour roux, which means it never turns out thin or grainy. Whole milk and a splash of cream give it body without making the dish feel heavy, and a spoonful of Dijon mustard brings a gentle warmth that works beautifully with the mild fish.

That buttery panko crust on top is not an afterthought. It bakes up golden and crisp, so every bite has that soft, creamy fish layer followed by a satisfying crunch. It is the kind of contrast that keeps you going back for one more forkful.

I love how relaxed this recipe is. You make a quick sauce, nestle in the fish, sprinkle on the topping, and let the oven do the rest. No fussing at the stove and no special skills needed.

Ingredients

• 1.5 lbs cod fillets: fresh works best; if using frozen, thaw completely and pat very dry
• 2 tbsp butter: for the sauce
• 1 small onion, finely diced: yellow or white
• 2 cloves garlic, minced
• 2 tbsp all-purpose flour
• 1 cup whole milk
• 1/2 cup heavy cream: 35% fat; makes the sauce extra velvety
• 1 tsp Dijon mustard
• 1/2 tsp dry mustard powder: optional, but it boosts that classic Newfoundland flavor
• 1 cup shredded sharp cheddar: plus a little extra for the top if you like
• 1/2 cup panko breadcrumbs: the light, flaky kind give the best crunch
• 2 tbsp melted butter: for the breadcrumb topping
• Salt and black pepper
• Lemon wedges: for serving

Variations / Substitutions

• Swap the cod: haddock, halibut, or any firm white fish works; avoid delicate fish that will fall apart.
• Change the cheese: a mix of cheddar and Gruyère melts beautifully if you want a nuttier note.
• Use a different crunch: crushed saltine crackers or Ritz crumbs make a fantastic old-fashioned topping.
• Add a little heat: a pinch of cayenne or a few dashes of hot sauce in the sauce wakes everything up.
• Dairy-free option: use unsweetened oat milk for the sauce and a mild vegan cheddar; the texture will be slightly thinner.

For more Newfoundland comfort food, try our recipe for Newfoundland Fish Cakes.

How to Make Newfoundland Cod Au Gratin

Step 1: Make the Sauce

Preheat your oven to 400°F (200°C) while you get the sauce started. In a medium saucepan, melt the 2 tbsp butter over medium heat, then add the diced onion and cook for about 4 minutes until soft and translucent. Stir in the garlic and cook 30 seconds more, just until it smells fragrant.

Sprinkle the 2 tbsp flour over the onion mixture and stir constantly for a full minute. This step cooks out the raw flour taste so your sauce comes out smooth. The paste will look a little dry and pale gold.

Step 2: Whisk in the Dairy

Pour in the 1 cup whole milk and the 1/2 cup heavy cream while whisking steadily. Keep the heat at medium-low and whisk until the mixture thickens enough to coat the back of a spoon, about 3 to 4 minutes. You will feel it tighten up as you stir, and the surface should hold light trails.

Remove the pan from the heat and stir in the Dijon mustard, dry mustard powder, half the shredded cheddar, and a good pinch of salt and pepper. Taste the sauce at this point. It should be nicely seasoned and sharp from the cheese, because the fish will mellow it out during baking.

Step 3: Layer the Casserole

Pat the cod fillets completely dry with paper towels and season both sides lightly with salt. Lay them in a single layer in a buttered 8×8-inch baking dish (or a similar shallow casserole). It is fine if the pieces overlap a little.

Pour the warm sauce evenly over the fish, using a spatula to spread it right to the edges so no bare spots dry out. Sprinkle the remaining cheddar over the top, then set the dish aside while you make the crumb topping.

Step 4: Bake and Serve

In a small bowl, mix the 1/2 cup panko breadcrumbs with the 2 tbsp melted butter and a tiny pinch of salt. Scatter this mixture evenly over the cheese layer, then slide the dish into the oven. Bake for 22 to 25 minutes, until the sauce is bubbling around the edges and the breadcrumbs are deep golden brown.

Let the dish rest on the counter for 5 minutes before serving. This short pause helps the sauce set up just enough that it does not run all over the plate. Spoon portions onto warm plates with a big wedge of lemon on the side and a crack of black pepper on top.

Tips for the Best Cod Au Gratin

• Pat the cod really dry. Any extra water will thin the sauce and make the casserole watery.
• Use freshly shredded cheese. Pre-shredded bags have anti-caking agents that keep the sauce from melting as smoothly.
• For an even crunchier top, broil the dish for 1 minute at the end. Watch it closely because the breadcrumbs can burn fast.
• If your sauce ever goes lumpy, a quick whisk off the heat or a pass through a fine strainer fixes it right up.

Bake times by cod thickness:

Storing Leftovers

• Refrigerate: Cool the dish completely, then cover and store in the fridge for up to 3 days. The sauce will firm up as it chills.
• Reheating: Warm individual portions in a 350°F oven for 12 to 15 minutes until heated through. The microwave works in a pinch, but the breadcrumb topping will soften.

What to Serve with Newfoundland Cod Au Gratin

Boiled baby potatoes with a pat of butter are the natural partner here; they soak up any extra sauce beautifully. A simple green salad dressed with lemon vinaigrette cuts through the richness, and steamed green beans or peas add a fresh, sweet pop that balances the casserole.

Frequently Asked Questions

Can I use salt cod instead of fresh?

Yes, but you need to soak the salt cod in cold water for 12 to 24 hours, changing the water a few times. After soaking, simmer it in fresh water for 10 minutes, then drain and flake before layering it in the dish.

Is it okay to assemble this the night before?

Absolutely. Prepare everything through the sauce and cheese layers, cover, and refrigerate for up to 12 hours. Add the breadcrumb topping just before baking so it stays crunchy.

What can I use if I do not have heavy cream?

Replace the heavy cream with an equal amount of whole milk. The sauce will be a little less rich, but it still turns out creamy and delicious.

How do I stop the breadcrumbs from getting soggy?

Tossing them with melted butter before they hit the casserole is key. That coating helps the crumbs crisp up while the fish cooks underneath.

My sauce tastes too sharp. How can I fix it?

Stir in a tiny pinch of sugar or a splash more cream. Different cheddars vary in sharpness, so a small adjustment before baking usually mellows things out.

Newfoundland Cod Au Gratin Recipe

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Prep Time 15 minutes mins

Cook Time 25 minutes mins

Total Time 40 minutes mins

Servings: 4 servings

Calories: 390

Ingredients Method Notes

Ingredients

  

• 1.5 lbs cod fillets
• 2 tbsp butter
• 1 small onion, finely diced
• 2 cloves garlic, minced
• 2 tbsp all-purpose flour
• 1 cup whole milk
• 1/2 cup heavy cream
• 1 tsp Dijon mustard
• 1/2 tsp dry mustard powder
• 1 cup shredded sharp cheddar, divided
• 1/2 cup panko breadcrumbs
• 2 tbsp melted butter
• Salt and black pepper
• Lemon wedges for serving

Method

 

1. Preheat oven to 400°F. Melt 2 tbsp butter in a saucepan over medium heat. Cook onion until soft, about 4 minutes. Add garlic and cook 30 seconds. Stir in flour and cook 1 minute.
2. Whisk in milk and cream. Cook, whisking, until thickened, 3 to 4 minutes. Remove from heat and stir in mustard, dry mustard, half the cheddar, and salt and pepper to taste.
3. Pat cod dry, season with salt, and place in a buttered baking dish. Pour sauce over fish, sprinkle remaining cheddar on top.
4. Mix panko with 2 tbsp melted butter and a pinch of salt. Scatter over casserole. Bake 22 to 25 minutes until bubbly and golden. Rest 5 minutes, then serve with lemon wedges.

Notes

Let the casserole sit for those 5 minutes before you scoop it out; this short rest gives the sauce time to settle so it coats the fish instead of running all over the plate. If you want a little extra color on top, run the dish under the broiler for a minute at the very end.