Tuna Tetrazzini

Looking for that perfect weeknight dinner that feels like a warm hug? This Tuna Tetrazzini is about to become your new comfort food MVP. Creamy, satisfying, and ridiculously easy to pull together—it’s the casserole that proves canned tuna can absolutely steal the show.

What makes this dish special is the magical combination of tender spaghetti, flaky tuna, and a velvety mushroom sauce that comes together in one beautiful baking dish. The contrast between the creamy interior and that golden, crunchy breadcrumb topping creates the kind of texture experience that has everyone scraping their plates clean. Trust me, you’ll want to make extra—this one disappears fast!

Ingredients

For the base:

• 8 oz spaghetti
• 2 tablespoons butter
• 1 small red onion, finely diced
• 2 cups crimini mushrooms, sliced
• 2 garlic cloves, pressed
• 1 teaspoon dried parsley

For the sauce:

• ¼ cup all-purpose flour
• 2½ cups milk
• ¼ teaspoon freshly ground black pepper
• Salt to taste

For the filling:

• 3 cans (5 oz each) tuna in olive oil, drained
• ½ cup frozen peas

For topping:

• 4 tablespoons breadcrumbs

Steps

1. Bring a large pot of water to a boil and cook the pasta al dente according to the instructions on the package, typically 7-8 minutes. For best results, cook it 1 minute less than package directions since it will continue cooking in the oven.
2. While the pasta cooks, melt the butter in a large pan over medium heat and sauté the red onion for 3-4 minutes until softened and translucent. You’ll know they’re ready when they become slightly transparent but not browned.
3. Add the mushrooms and continue to cook for 5-6 minutes until they’ve released their moisture and developed a rich brown color. Don’t rush this step—properly browned mushrooms provide deeper flavor.
4. Meanwhile, preheat the oven to 350°F (175°C) and lightly spray a 9×13 inch baking dish with cooking spray, then set aside. The spray prevents sticking and makes cleanup easier.
5. When the mushrooms are cooked, stir in the garlic and parsley, then whisk in the flour. Cook for 1 minute while whisking often. The mixture will look paste-like—this is your roux and it’s essential for thickening the sauce.
6. Stir in the milk in batches (about ½ cup at a time), whisking constantly until you have a thick and smooth mixture. This gradual addition prevents lumps from forming. The sauce should coat the back of a spoon when it’s the right consistency.
7. Season with salt and freshly ground black pepper, then turn off the heat. Taste and adjust seasonings as needed—proper seasoning at this stage is crucial.
8. Add the drained tuna (breaking it into flakes with a fork) and frozen peas (no need to thaw) and stir to combine. Toss the cooked pasta in the sauce using kitchen tongs until every strand is evenly coated.
9. Transfer the mixture to the prepared baking dish and make sure it’s evenly layered. Top with breadcrumbs, spreading them in an even layer. For extra richness, you can dot the top with 1 tablespoon of butter cut into small pieces.
10. Bake for 15 minutes or until the breadcrumbs become golden and the edges are bubbling. If your breadcrumbs aren’t browning enough, switch to the broiler for the final 1-2 minutes, watching carefully to prevent burning.
11. Allow the dish to stand for 5-10 minutes before serving. This resting period helps the sauce set slightly, making it easier to portion and serve.

Smart Swaps

• Use whole wheat spaghetti instead of regular for added fiber (same cooking time, slightly nuttier flavor)
• Substitute 1 cup grated Parmesan mixed with the breadcrumbs for an extra cheesy crust
• Try canned salmon instead of tuna for a different flavor profile and added omega-3s
• Replace ½ cup of milk with ½ cup dry white wine for a more sophisticated flavor profile

Make It Diabetes-Friendly

• Use whole grain pasta instead of regular spaghetti to reduce the glycemic impact (reduces approximately 10g carbs per serving)
• Replace regular milk with unsweetened almond milk and add 2 tablespoons of cream cheese for richness (reduces approximately 8g carbs per serving)
• Increase the peas to 1 cup and add 1 cup diced bell peppers for more fiber and nutrients without significantly increasing carbs
• Serve with a side salad dressed with olive oil and vinegar to slow carbohydrate absorption

Pro Tips

• For the creamiest sauce, make sure your milk is at room temperature before adding it to the roux
• Don’t rinse the pasta after cooking—the starch helps the sauce cling better
• For extra flavor, add ¼ teaspoon of nutmeg to the sauce
• This casserole freezes beautifully—portion into individual containers for quick weeknight meals that reheat in the microwave in 3-4 minutes