Tuna Au Gratin

Creamy, cheesy, and irresistibly comforting, Tuna Au Gratin is the ultimate baked casserole dish that delivers indulgent flavor with minimal effort—perfect for weeknight dinners or casual gatherings. This recipe combines tender flakes of canned tuna with a velvety cheese sauce featuring sharp cheddar and Parmesan, layered under a golden, crunchy breadcrumb topping. Infused with Dijon mustard and a hint of garlic and onion powder, each bite balances richness and depth of flavor. Customize it by adding cooked pasta for a heartier twist, and finish with a sprinkle of fresh parsley for a pop of color. Quick to prep and ready in just 40 minutes, this crowd-pleasing classic is a harmonious blend of creamy textures and crispy perfection. Ideal for those craving an easy yet elevated comfort food experience!

Nutriscore Rating: 58/100

Prep Time:15 mins

Cook Time:25 mins

Total Time:40 mins

Servings: 4

Ingredients

• 2 cans (5 oz each) canned tuna
• 4 tablespoons butter
• 3 tablespoons all-purpose flour
• 2 cups milk
• 1.5 cups (shredded) sharp cheddar cheese
• 0.5 cups (grated) Parmesan cheese
• 0.75 cups breadcrumbs
• 1 teaspoon Dijon mustard
• 0.5 teaspoons garlic powder
• 0.5 teaspoons onion powder
• 1 teaspoon (adjust to taste) salt
• 0.5 teaspoons black pepper
• 2 cups (optional, for a heartier dish) cooked pasta
• 2 tablespoons (optional, for garnish) chopped parsley

Directions

Step 1

Preheat your oven to 375°F (190°C). Lightly grease a 9x9-inch baking dish or similar-sized casserole dish.

Step 2

Drain the canned tuna and flake it with a fork. Set aside.

Step 3

In a medium saucepan, melt 3 tablespoons of butter over medium heat. Once melted, whisk in the all-purpose flour to create a roux. Cook for 1-2 minutes, stirring constantly, until the mixture begins to bubble.

Step 4

Gradually pour in the milk while whisking to avoid lumps. Cook over medium heat until the mixture begins to thicken into a smooth sauce, about 3-5 minutes.

Step 5

Reduce the heat to low and stir in the Dijon mustard, garlic powder, onion powder, salt, and black pepper. Mix well.

Step 6

Add the shredded sharp cheddar cheese and grated Parmesan cheese to the sauce, reserving a small handful of Parmesan for topping later. Stir until the cheese is melted and the sauce is smooth.

Step 7

Fold the flaked tuna into the cheese sauce. If using cooked pasta, mix it in at this stage as well.

Step 8

Pour the tuna mixture into the prepared baking dish, spreading it out evenly.

Step 9

In a small bowl, melt the remaining tablespoon of butter and mix it with the breadcrumbs. Add the reserved Parmesan cheese and toss to combine.

Step 10

Sprinkle the breadcrumb mixture evenly over the top of the tuna mixture in the baking dish.

Step 11

Bake in the preheated oven for 20-25 minutes, or until the topping is golden brown and the filling is bubbling around the edges.

Step 12

Remove from the oven and let rest for 5 minutes before serving. Optionally, garnish with chopped parsley for a fresh finish.

Step 13

Serve warm and enjoy your homemade Tuna Au Gratin!

Nutrition Facts

Serving size	1370.9 grams (1370.9g)

Amount per serving	% Daily Value*
Calories	2595

Total Fat 135.30g	173%
Saturated Fat 78.80g	394%
Polyunsaturated Fat 1.80g
Cholesterol 502mg	167%
Sodium 6471mg	281%
Total Carbohydrate 175.30g	64%
Dietary Fiber 7.90g	28%
Total Sugars 31.10g
Protein 174.30g	349%

Vitamin D 451IU	2253%
Calcium 2392mg	184%
Iron 11mg	63%
Potassium 1479mg	31%

*The % Daily Value tells you how much a nutrient in a serving of food contributes to a daily diet. 2,000 calories a day is used for general nutrition advice.

Source of Calories

Fat: 46.5%

Protein: 26.7%

Carbs: 26.8%