Turkey Tetrazzini with Mushrooms

There's something about the way a casserole dish hits the table that makes everyone pause mid-conversation. Years ago, my neighbor brought over her turkey tetrazzini after Thanksgiving, and I watched my family devour it in minutes—something about that creamy, golden-topped comfort just hit different. That's when I realized the magic wasn't in having leftovers; it was in knowing exactly what to do with them. Now this dish is my answer to the question I get asked every November: what do you do with all that turkey?

I made this for a potluck once and watched my coworker take three bites before asking for the recipe—she had the look of someone who'd just discovered their new weeknight favorite. What surprised me most was how the peas add this unexpected sweetness that balances the earthiness of the mushrooms, creating something that tastes far more sophisticated than its simple ingredient list suggests. It's become the dish I bring when I want to impress without showing off.

Ingredients

• Spaghetti or linguine (340 g / 12 oz): The pasta is your foundation—cook it just shy of tender so it doesn't turn to mush when it bakes, which is easier said than done but worth the attention.
• Unsalted butter (4 tbsp): This is your starting point for building flavor, so don't skip it or swap it for oil.
• Yellow onion (1 medium, finely chopped): It melts into the sauce and becomes invisible but essential, like a good supporting actor.
• Garlic (3 cloves, minced): Fresh garlic makes all the difference; jarred stuff gets bitter when baked, so this is worth the thirty seconds.
• Cremini or white mushrooms (250 g / 9 oz, sliced): These earthy little powerhouses are the soul of this dish—they absorb and release flavor as they cook, giving the whole thing depth.
• All-purpose flour (4 tbsp): This thickens your sauce and creates the roux; whisk it in smoothly to avoid lumps.
• Whole milk, broth, and heavy cream (720 ml / 3 cups milk, 120 ml / 1/2 cup broth, 120 ml / 1/2 cup cream): The trio that makes the sauce silky—the milk is your bulk, the broth adds savory depth, and the cream adds richness that makes you close your eyes.
• Kosher salt, black pepper, and nutmeg (1/2 tsp salt, 1/4 tsp pepper, 1/4 tsp nutmeg): A whisper of nutmeg in a cream sauce is the secret handshake of good cooking.
• Cooked turkey (400 g / 3 cups, shredded or diced): Use whatever you have—shredded works better for texture, but diced is fine too.
• Frozen peas (180 g / 1 cup, thawed): Thaw them first so they don't deflate into the sauce while everything bakes.
• Parmesan cheese (70 g / 3/4 cup grated): Grate it fresh if you can; the pre-grated stuff has anti-caking agents that make sauces grainy.
• Shredded mozzarella (120 g / 1 cup): This melts into the filling and makes it cohesive, while Parmesan brings the sharpness.
• Fresh parsley (2 tbsp chopped): The brightness at the end that makes it taste alive instead of heavy.
• Panko breadcrumbs (60 g / 1 cup): Panko stays crispier than regular breadcrumbs, and that matters for your topping.
• Melted butter (2 tbsp) and Parmesan (2 tbsp): For the topping, because carbs and cheese together are non-negotiable.

Instructions

Get your oven ready:

Preheat to 190°C (375°F) and grease your 23x33 cm baking dish—this temperature is hot enough to brown the top without drying out the filling.

Cook the pasta:

Boil your spaghetti or linguine in salted water until it's just al dente, then drain it well. It'll keep cooking in the oven, so don't let it get soft now.

Build the sauce base:

In a large skillet, melt the butter over medium heat and add your finely chopped onion. Let it soften for about 3 minutes—you want it translucent and sweet, not browned. Add the garlic and cook for another minute until it smells incredible.

Add the mushrooms:

Toss in your sliced mushrooms and let them sauté for 6–8 minutes, stirring occasionally, until they're golden and any liquid they release has evaporated. This is when your kitchen starts to smell like a fancy restaurant.

Make the roux:

Sprinkle the flour over your vegetables and stir constantly for 1–2 minutes. You're creating a paste that will thicken your sauce, and this step matters because it prevents lumps later.

Add the creamy liquid:

Slowly whisk in the milk, broth, and cream, stirring constantly to keep everything smooth. Bring it to a gentle simmer and keep stirring for about 5 minutes until the sauce thickens enough to coat a spoon. This is patience rewarded.

Season and finish the sauce:

Remove from heat and taste it—add salt, pepper, and just a pinch of nutmeg. That nutmeg is quiet but important, rounding out the flavors without announcing itself.

Combine everything:

Stir in your cooked turkey, thawed peas, both cheeses, parsley, and the cooked pasta. Mix until evenly combined so every bite has a little bit of everything. This is where it comes together.

Transfer to the baking dish:

Pour your mixture into the prepared dish and spread it out evenly.

Make the topping:

In a small bowl, mix the panko breadcrumbs with melted butter and Parmesan until it's crumbly and moistened. Sprinkle this over the entire casserole.

Bake until golden:

Bake uncovered for 25–30 minutes, until the top is golden brown and you can see the filling bubbling at the edges. Your kitchen will smell like comfort.

Rest before serving:

Let it sit for 10 minutes—this isn't wasted time, it's when the sauce sets up and everything becomes cohesive instead of soupy. Garnish with extra parsley if you want that final touch.

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There was a moment when my daughter asked if we could make this instead of cooking a whole new turkey one year, and I realized this dish had become more about comfort than necessity. That's when you know you've found something worth holding onto.

Variations and Swaps

Use rotisserie chicken instead of turkey—nobody will know and everyone will be happy. Add a splash of dry sherry or white wine to the sauce for complexity, stirring it in after you remove the pan from heat so the alcohol cooks off but the flavor stays. For a crispier, almost-broiled topping, slide the whole thing under the broiler for 2–3 minutes at the end, watching it closely so the breadcrumbs toast instead of burn.

Make It Ahead

Assemble this entire casserole up to a day before baking, cover it with foil, and refrigerate—just add 10 minutes to your baking time since you're starting from cold. You can even freeze it unbaked for up to three months, though you'll want to thaw it in the fridge overnight before cooking. The beauty of a casserole is that it rewards planning.

Serving Suggestions and Kitchen Notes

Serve this alongside a simple green salad dressed with lemon vinaigrette to cut through the richness, or with roasted vegetables if you want something more substantial. A glass of white wine pairs beautifully—something crisp like a Sauvignon Blanc. Leftovers reheat gently in a 160°C oven covered with foil, and honestly, they might taste even better the next day when all the flavors have settled into each other.

• If your sauce looks too thin before baking, mix a tablespoon of cornstarch with cold water and whisk it in—it thickens quickly.
• Keep the parsley fresh and add it right before serving rather than mixing it into the casserole.
• This makes enough for 6 generous servings, but it freezes well if you want to make extra.

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This is the kind of dish that feeds more than just your hunger—it's what you make when you want to turn an ordinary evening into something that feels intentional. Keep it in your back pocket for when you need dinner that tastes like you spent all day cooking.

Recipe Questions & Answers

→ What pasta works best in this dish?

Spaghetti or linguine both work well, cooked al dente to hold up under the creamy sauce and baking process.

→ Can I substitute chicken for turkey?

Yes, rotisserie chicken can be used as a flavorful alternative and will blend nicely with the sauce and vegetables.

→ How can I achieve a crispier topping?

Broil the casserole for 2-3 minutes at the end of baking to brown the panko and cheese topping further.

→ Is there an option for a gluten-free version?

Use gluten-free pasta and substitute all-purpose flour with a gluten-free alternative to make the dish gluten-free.

→ What adds depth of flavor to the sauce?

A splash of dry sherry or white wine can be added to the sauce to enhance the overall taste complexity.