Creamy Tuna Potato Casserole with Peas and Crunchy Topping

Quick Recipe Version (TL;DR)

• Yield: 6 servings
• Prep Time: 25 minutes
• Cook Time: 45 minutes
• Total Time: 1 hour 10 minutes

Quick Ingredients

• 2 lb (900 g) potatoes, peeled and sliced 1/4 inch thick
• 2 (5 oz / 142 g) cans tuna in water, drained and flaked
• 1 cup frozen peas, thawed and drained
• 2 tbsp butter (for sauce) + 2 tbsp butter (for topping)
• 1 small onion, finely chopped; 2 garlic cloves, minced
• 3 tbsp all-purpose flour
• 1 3/4 cups milk + 1/2 cup low-sodium chicken or vegetable broth
• 1/3 cup sour cream or plain Greek yogurt
• 3/4 cup shredded sharp cheddar cheese
• 3/4 cup panko breadcrumbs + 1/4 cup crushed plain potato chips
• 1/4 cup grated Parmesan cheese
• 1 tsp Dijon mustard, 1/2 tsp dried thyme, 1/2 tsp smoked paprika
• About 1 1/4 tsp kosher salt and 1/2 tsp black pepper, divided

Do This

• 1. Heat oven to 375°F (190°C). Grease a 9×13-inch (3 L) baking dish.
• 2. Boil sliced potatoes in salted water 8–10 minutes until just tender; drain well.
• 3. In a saucepan, sauté onion in 2 tbsp butter, add garlic, then flour. Whisk in milk and broth with mustard, thyme, salt, and pepper; simmer until slightly thick.
• 4. Off heat, stir in sour cream or yogurt and cheddar until smooth. Adjust seasoning.
• 5. In a large bowl, gently toss potatoes with tuna, peas, and sauce. Spread evenly in baking dish.
• 6. Mix panko, crushed chips, Parmesan, paprika, salt, pepper, and melted butter; sprinkle over casserole.
• 7. Bake 30–35 minutes, until bubbling and golden. Rest 10 minutes before serving.

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Why You’ll Love This Recipe

• Classic, cozy tuna casserole vibes with a fresher update: lighter creamy sauce, not too heavy or gloopy.
• Comforting layers of tender potatoes, flaky tuna, and sweet peas under a seriously crunchy, golden topping.
• Uses simple pantry staples, canned tuna, and frozen peas for an easy, budget-friendly bake.
• Perfect make-ahead family dinner that reheats beautifully and feeds a crowd.

Grocery List

• Produce: Potatoes, yellow onion, garlic, fresh parsley (optional, for garnish)
• Dairy: Butter, milk, sour cream or plain Greek yogurt, sharp cheddar cheese, Parmesan cheese
• Pantry: Canned tuna in water, frozen peas, all-purpose flour, low-sodium chicken or vegetable broth, panko breadcrumbs, plain potato chips, Dijon mustard, dried thyme, smoked or sweet paprika, kosher salt, black pepper

Full Ingredients

For the Casserole Base

• 2 lb (900 g) waxy or all-purpose potatoes (Yukon Gold or red), peeled and sliced 1/4 inch (6 mm) thick
• 2 (5 oz / 142 g) cans tuna in water, well drained and flaked (about 10 oz / 280 g total)
• 1 cup (140 g) frozen peas, thawed and drained

For the Light Creamy Sauce

• 2 tbsp (28 g) unsalted butter
• 1 small yellow onion, finely chopped (about 1 cup / 120 g)
• 2 garlic cloves, minced
• 3 tbsp (24 g) all-purpose flour
• 1 3/4 cups (420 ml) milk (2% or whole)
• 1/2 cup (120 ml) low-sodium chicken or vegetable broth
• 1 tsp Dijon mustard
• 1/2 tsp dried thyme
• 3/4 tsp kosher salt (or 1/2 tsp fine sea salt), plus more to taste
• 1/4 tsp freshly ground black pepper, plus more to taste
• 1/3 cup (80 g) sour cream or plain Greek yogurt (2% or whole milk)
• 3/4 cup (75 g) shredded sharp cheddar cheese, lightly packed

For the Crunchy Topping

• 3/4 cup (45 g) panko breadcrumbs
• 1/4 cup (about 20 g) crushed plain potato chips (roughly crushed, not powdered)
• 1/4 cup (25 g) finely grated Parmesan cheese
• 2 tbsp (28 g) unsalted butter, melted
• 1/4 tsp smoked paprika (or sweet paprika)
• 1/4 tsp kosher salt
• 1/4 tsp freshly ground black pepper

Optional for Serving

• 2 tbsp chopped fresh parsley or chives, for garnish
• Extra black pepper at the table

Step-by-Step Instructions

Step 1: Prep the Oven, Dish, and Ingredients

Preheat your oven to 375°F (190°C) with a rack in the center. Lightly grease a 9×13-inch (about 3 L) baking dish with butter or nonstick spray.

Peel the potatoes and slice them into 1/4 inch (6 mm) thick rounds. Try to keep the slices even so they cook at the same rate. Finely chop the onion and mince the garlic. If your peas are frozen, measure out 1 cup and let them sit at room temperature or in a bowl of lukewarm water to thaw, then drain well.

Step 2: Parboil the Potatoes

Place the sliced potatoes in a large pot and cover with cold water by about 1 inch (2.5 cm). Add 1 tsp of kosher salt to the water. Bring to a boil over high heat, then reduce to a gentle simmer.

Cook for 8–10 minutes, until the potatoes are just barely tender when pierced with the tip of a knife but still holding their shape. You do not want them fully soft or they will fall apart in the casserole. Drain the potatoes carefully in a colander and let them sit for a few minutes to steam-dry so excess moisture evaporates.

Step 3: Start the Light Creamy Sauce

While the potatoes simmer, make the sauce. In a medium saucepan, melt 2 tbsp butter over medium heat. Add the chopped onion and cook, stirring occasionally, for 5–7 minutes until softened and translucent but not browned.

Add the minced garlic and cook for 30 seconds, just until fragrant. Sprinkle the flour evenly over the onions and garlic. Stir continuously for 1 minute; the mixture will become thick and pasty. This step cooks off the raw flour taste and forms the base of your light cream sauce.

Step 4: Finish the Sauce with Milk, Broth, and Cheese

Gradually whisk in the milk and broth, a little at a time, whisking well after each addition to smooth out any lumps. Once all the liquid is in, stir in the Dijon mustard, dried thyme, 3/4 tsp kosher salt, and 1/4 tsp black pepper.

Bring the mixture to a gentle simmer, whisking frequently, until it thickens slightly and coats the back of a spoon, about 3–5 minutes. Remove the saucepan from the heat. Stir in the sour cream or Greek yogurt until smooth, then add the shredded cheddar cheese. Stir until the cheese is melted and the sauce is velvety and pourable. Taste and adjust seasoning with a little more salt or pepper if needed; it should be well seasoned, as it will flavor all the potatoes and tuna.

Step 5: Combine Potatoes, Tuna, Peas, and Sauce

In a large mixing bowl, add the drained, flaked tuna and the thawed, drained peas. Gently toss to distribute the peas through the tuna. Add the parboiled potato slices to the bowl.

Pour the warm creamy sauce over the potatoes, tuna, and peas. Using a large spoon or spatula, very gently fold everything together until the sauce lightly coats all the ingredients. Try not to break up the potatoes too much; some smaller pieces are fine, but you still want distinct slices and flakes of tuna.

Transfer the mixture to your prepared baking dish, spreading it out into an even layer and gently smoothing the top.

Step 6: Make the Crunchy Topping

In a medium bowl, combine the panko breadcrumbs, crushed potato chips, grated Parmesan, smoked paprika, 1/4 tsp kosher salt, and 1/4 tsp black pepper. Stir to mix everything evenly.

Drizzle the melted butter over the mixture. Toss with a fork or your fingers until all the crumbs are lightly coated and look evenly moistened; this helps them toast up beautifully golden and crunchy instead of dry.

Sprinkle the topping evenly over the casserole, covering the surface from corner to corner so every bite gets some crunch.

Step 7: Bake Until Bubbling and Golden

Cover the casserole loosely with foil, tenting it slightly so it does not press on the topping. Bake at 375°F (190°C) for 15 minutes to heat everything through without over-browning the crumbs.

Remove the foil and continue baking for another 15–20 minutes, until the casserole is bubbling around the edges and the topping is deep golden brown and crisp. Total bake time will be about 30–35 minutes.

Let the casserole rest on a cooling rack for at least 10 minutes before serving. This short rest helps the sauce thicken slightly and makes it easier to scoop neat portions. Sprinkle with chopped fresh parsley or chives if using, and serve warm.

Pro Tips

• Do not overcook the potatoes. Take them off the heat as soon as they are just tender. If they get too soft, they will turn mushy in the oven and the casserole will lose its nice texture.
• Drain the tuna thoroughly. Press the tuna gently against the side of the can with a fork to remove excess liquid. Too much moisture can make the sauce watery.
• Season the sauce generously. The sauce is what flavors all the potatoes and tuna, so taste it before you combine everything and adjust with extra salt, pepper, or mustard if it tastes bland.
• Keep the sauce light but creamy. It should coat the back of a spoon but still flow easily. If it seems too thick, whisk in 1–2 tbsp of extra milk. If it is too thin, simmer a couple more minutes.
• Watch the topping near the end. Ovens vary. If the topping is browning too quickly, loosely tent with foil. If it is too pale at 30 minutes, give it a few extra minutes on the top rack.

Variations

• Extra-cheesy version: Increase the cheddar to 1 cup (100 g) in the sauce and sprinkle an additional 1/2 cup (50 g) cheddar directly on the casserole before adding the breadcrumb topping for a gooier, more indulgent bake.
• Herby lemon twist: Add 1 tsp finely grated lemon zest and 2 tbsp chopped fresh parsley to the sauce off the heat. The bright citrus and fresh herbs lift the flavors and pair beautifully with tuna and peas.
• Chicken or salmon swap: Replace the tuna with the same amount of cooked, shredded chicken or flaked cooked salmon for a different but equally comforting casserole.

Storage & Make-Ahead

Let any leftovers cool to room temperature, then cover the dish tightly or transfer portions to airtight containers. Store in the refrigerator for up to 3 days. Reheat individual portions in the microwave until hot, or rewarm the whole casserole, covered, in a 325°F (165°C) oven for 20–25 minutes, then uncover for the last 5 minutes to re-crisp the topping.

To make ahead, assemble the casserole completely, including the topping, cover tightly, and refrigerate for up to 24 hours before baking. When ready to cook, bake straight from the fridge at 375°F (190°C), adding 5–10 minutes to the covered baking time. For longer storage, you can freeze the assembled, unbaked casserole (well wrapped) for up to 2 months. Thaw overnight in the fridge before baking. Note that the topping may absorb a bit more moisture after freezing, but will still be pleasantly crunchy once baked.

Nutrition (per serving)

Approximate values for 1 of 6 servings: about 470 calories; 20 g protein; 20 g fat; 43 g carbohydrates; 4 g fiber; 7 g saturated fat; 120 mg cholesterol; around 900 mg sodium. These numbers are estimates and will vary based on the exact brands and ingredients you use.