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Tuna Mornay with Crunchy Chip Topping

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Prep Time: 20 minutes
Cook Time: 25 minutes
Total Time: 45 minutes
Serves: 4-6
Skill Level: Easy
Effort Intensity: Moderate (involves making a roux-based sauce)
Cost: Budget-Friendly
Dietary Notes: Easily adaptable to gluten-free

A Note From Our Kitchen

Tuna Mornay is the epitome of nostalgic comfort food. Our version elevates the classic with a secret weapon: a crispy, crunchy potato chip topping that provides the perfect textural contrast to the rich, creamy sauce below. It’s a hearty, satisfying dish that turns simple pantry staples into a memorable meal.

Ingredients

For the Tuna Mornay Filling:

  • 50g (3.5 tbsp) butter

  • 1 medium onion, finely diced

  • 2 celery stalks, finely diced

  • 50g (½ cup) plain all-purpose flour

  • 500ml (2 cups + 2 tbsp) milk, warmed

  • 125ml (½ cup) vegetable or chicken stock

  • 1 tbsp Dijon mustard

  • 1 cup grated vintage cheddar cheese, divided

  • ½ cup frozen peas

  • 2 x 185g (6.5oz) cans of tuna in springwater, drained and flaked

  • Salt and freshly ground black pepper to taste

  • Pinch of nutmeg (optional)

For the Crunchy Chip Topping:

  • 150g (5oz) plain potato chips (crisps), lightly crushed

  • 30g (¼ cup) grated vintage cheddar cheese

  • 1 tbsp finely chopped parsley (optional)

You’ll Also Need:

  • A large saucepan or Dutch oven

  • Whisk

  • 2-3 litre (approx. 2-3 quart) ovenproof baking dish

Instructions

Step 1: Prepare & Preheat

Preheat your oven to 200°C (390°F) or 180°C (350°F) for fan-forced. Lightly grease your baking dish.

Step 2: Build the Flavor Base

Melt the butter in your large saucepan over medium heat. Add the diced onion and celery, cooking for 5-7 minutes until softened and translucent but not browned. This builds a sweet, aromatic foundation for your sauce.

Step 3: Create the Roux

Sprinkle the flour over the cooked vegetables. Stir constantly with a wooden spoon for 1-2 minutes until the mixture forms a paste (the roux) and takes on a very light golden color. This cooks out the raw flour taste.

Step 4: Make the Béchamel Sauce

Gradually add the warm milk, about a quarter at a time, whisking vigorously after each addition until the mixture is completely smooth before adding more. Once all the milk is incorporated, add the stock and Dijon mustard. Continue to cook, stirring constantly, for 5-7 minutes until the sauce has thickened nicely to a coat-the-back-of-a-spoon consistency.

Chef’s Tip: Using warm milk prevents lumps from forming in your sauce!

Step 5: Finish the Mornay Filling

Remove the saucepan from the heat. Stir in three-quarters (¾ cup) of the grated cheddar until melted and smooth. Season well with salt, pepper, and a pinch of nutmeg if using. Gently fold in the frozen peas and flaked tuna until evenly distributed. Taste and adjust seasoning.

Step 6: Assemble & Top

Pour the creamy tuna mixture into your prepared baking dish, spreading it out evenly. Sprinkle the remaining ¼ cup of grated cheese over the surface. In a small bowl, mix the lightly crushed potato chips with the 30g of cheese (and parsley, if using). Scatter this crunchy mixture evenly over the entire top of the mornay.

Step 7: Bake to Golden Perfection

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

Step 8: Rest & Serve

Remove from the oven and let it rest for 5 minutes before serving. This allows the sauce to settle slightly, making it easier to portion. Serve hot, scooped onto plates.

Serving Suggestions

  • Classic: Spooned over steamed rice or buttered pasta shells.

  • Low-Carb: Served alongside a big, fresh garden salad or steamed green beans.

  • Retro Vibes: With a side of buttered toast points or tucked into jaffle (toastie) makers for the ultimate crispy sandwich.

  • Garnish: A final sprinkle of fresh chives or parsley adds a pop of color and freshness.

Storage & Reheating

  • Storage: Cool completely, cover tightly, and refrigerate for up to 3 days.

  • Reheating: Reheat portions in the microwave until piping hot. For best topping results, re-crisp under a hot grill (broiler) for 1-2 minutes after microwaving.

  • Freezing: Freeze the unbaked, topped dish for up to 2 months. Thaw overnight in the refrigerator before baking as directed. You may need to add a few extra minutes to the bake time.

Nutrition Information (Per Serving, based on 6 servings)

  • Calories: ~520 kcal

  • Protein: 28g

  • Carbohydrates: 35g

  • (of which sugars): 8g

  • Fat: 28g

  • (of which saturates): 13g

  • Fiber: 3g

  • Sodium: ~850mg

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