Growing up in New England, my grandmother made haddock au gratin at least twice a month. It was her go-to dish whenever company came over, and now I know why. This creamy, cheesy baked fish dish is pretty much impossible to mess up, even for beginners in the kitchen. While some people shy away from cooking fish at home, this recipe changed my mind about how simple it can be. All you really need is some fresh haddock, a few basic ingredients from your pantry, and about 30 minutes of your time.
Suggestions for Ingredient Substitution
Haddock fillets can be replaced with cod, pollock, or tilapia for similar mild, white fish options. These alternatives maintain the dish’s texture and flavor profile while offering flexibility based on availability or personal preference. Adjust cooking time slightly for thicker or thinner fillets.
Heavy cream can be substituted with half-and-half or evaporated milk to reduce fat content. For a dairy-free option, use unsweetened coconut cream. Reduce the amount of milk in the recipe if using a thinner alternative to maintain the sauce’s consistency.
Breadcrumbs can be swapped with crushed pork rinds for a low-carb, gluten-free topping. Alternatively, use almond meal or finely chopped nuts for added texture and nutrients. Adjust the quantity as needed to achieve the desired coverage and crunch. These substitutions cater to various dietary needs while preserving the dish’s crispy topping.
| Preparation Time | 20-30 minutes |
| Cooking Time | 30-40 minutes |
| Total Time | 50-70 minutes |
| Level of Difficulty | Medium |
Estimated Nutrition
Estimated nutrition for the whole recipe (without optional ingredients):
- Calories: 600-700
- Protein: 50-60 g
- Fat: 40-50 g
- Carbohydrates: 30-35 g
Ingredients
For the fish:
- 2 haddock fillets (5-6 oz each)
- 1/2 tsp garlic salt
- ground black pepper (freshly ground preferred for more flavor)
For the sauce base:
- 1/3 cup heavy cream (gives better texture and richness)
- 1 tsp Dijon mustard (I use Grey Poupon)
- 1 tbsp melted butter
- 1/3 cup chicken broth
- 1/4 cup milk
For the sauce vegetables:
- 3 tbsp finely chopped red bell pepper
- 2.5 tbsp finely chopped onion
- 2 tbsp plain flour
- 1/3 cup sliced white mushrooms
- 2.5 tbsp shredded Parmesan cheese
- 2.5 tbsp finely chopped celery
- 2 tbsp butter (I like Kerrygold unsalted butter for this)
For the topping:
- 1/2 tbsp melted butter
- paprika
- 1/3 cup grated cheddar cheese
- 1/3 cup fine breadcrumbs
For garnish:
- green onions
Step 1: Prepare the Sauce Mixture
In a small bowl, combine chicken stock, whipping cream, milk, Dijon mustard, and 1 tablespoon of melted butter.
Mix well and set aside for later use.
This will be the base of your creamy sauce.
Step 2: Prepare Ingredients and Preheat Oven
Chop and measure your vegetables, and grate the cheeses.
Preheat your oven to 350°F.
Grease two individual-sized au gratin dishes or a small shallow baking dish—just large enough to arrange the fish fillets in a single layer.
Season the fish fillets with garlic salt and pepper.
If using individual dishes, you may need to trim the ends of the fillets to fit and arrange them alongside the main fillet.
Set the prepared dishes aside.
Step 3: Sauté the Vegetables
Melt 1½ – 2 tablespoons of butter in a saucepan over medium-high heat.
Add the onions, celery, red pepper, and mushrooms.
Cook them until they are barely tender, stirring frequently, which should take about 3 minutes.
Step 4: Make the Sauce
Sprinkle flour over the sautéed vegetables and stir to combine.
Cook for a few seconds, then reduce the heat to medium-low.
Gradually add the prepared chicken stock and cream mixture, stirring constantly to prevent scorching.
Continue cooking until the sauce starts to thicken, about 1-2 minutes.
Add Parmesan cheese and stir until melted, thickening the sauce to the desired consistency, approximately 1 minute longer.
Step 5: Assemble and Bake the Fish
Spoon the sauce equally over each fish fillet, covering them completely.
In a separate small bowl, combine breadcrumbs with ½ tablespoon of melted butter, then sprinkle this mixture evenly over the fillets.
Place the au gratin dishes on a foil-lined rimmed baking sheet, just in case the sauce bubbles over.
Bake for about 20-24 minutes or until the breadcrumbs are browned, the sauce is bubbling, and the fish is cooked through, flaking easily with a fork.
Note that baking times may vary depending on the size and thickness of the fillets.
Step 6: Add Finishing Touches and Serve
After baking, sprinkle cheddar cheese over each fillet and return them to the oven for 1½ – 2 minutes, just until the cheese is melted.
Allow the fish to stand for 5-10 minutes to let the sauce set.
Sprinkle each fillet with paprika and garnish with sliced green onions and an orange or lemon slice if desired.
Serve the fish with your choice of potato or rice and a favorite side of vegetables, whether steamed or stir-fried.
