Creamy Leftover Turkey Tetrazzini with Mushrooms

The mushrooms start releasing their liquid almost as soon as they hit the butter, and that’s the moment I watch most closely. Let them cook until the pan looks dry…

By Riley • October 25, 2026 • Reading time: 9 min

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The mushrooms start releasing their liquid almost as soon as they hit the butter, and that’s the moment I watch most closely. Let them cook until the pan looks dry and they’ve browned; otherwise, their extra moisture can leave the sauce loose. This creamy leftover turkey tetrazzini with mushrooms turns cooked turkey into a bubbling casserole with a crisp panko top.

I cook the spaghetti just shy of al dente because it gets another stretch in the oven, soaking up the Parmesan cream sauce as it bakes. The sauce begins with mushrooms and onion, then flour helps it thicken before the broth and cream go in. After that, turkey and peas get folded through, and the whole pan lands under a golden blanket of crumbs. The center stays creamy, and every scoop has a little crunch on top.

Why the Spaghetti Needs to Go Into the Oven Slightly Underdone

Spaghetti that’s already fully al dente before it meets the sauce has nowhere to go in the oven except softer. I stop cooking it two minutes before the package’s al dente timing, then drain it and combine it with the hot sauce. During the bake, the noodles take in some of that creamy sauce while the casserole heats through. That small head start keeps the finished pasta tender without turning it limp.

It also helps to think of the sauce and pasta as finishing together, not as two finished components being put in the same dish. The sauce should be thickened on the stovetop, but it still needs enough body to coat the noodles evenly before baking. If the pasta sits drained for a long time, it can stick together; have the sauce ready so you can combine everything while the noodles are still warm. That gives the casserole an even, creamy texture instead of dry strands with sauce pooled underneath.

What Gives This Tetrazzini Its Creamy Center and Crisp Top

• Spaghetti — Its long strands catch the sauce throughout the casserole. Standard dried spaghetti is a good fit here; save a little cooking time for the oven rather than boiling it all the way to al dente.
• Cremini mushrooms — They bring a deep, savory taste and brown well in the skillet. Fresh mushrooms matter more than a specialty variety: choose firm slices, and let their cooking liquid evaporate before moving on.
• Chicken broth and heavy cream — Broth keeps the sauce savory while cream gives it a rich, smooth base. Low-sodium broth leaves room for the measured salt and Parmesan; heavy cream is what makes this sauce lush, so a lighter milk won’t give the same body.
• All-purpose flour — Cooked briefly with the butter and vegetables, it thickens the broth and cream into a sauce that clings to the pasta. Stir it in thoroughly before adding liquid so you don’t leave dry pockets in the finished sauce.
• Freshly grated Parmesan — It melts directly into the sauce and brings a salty, nutty edge. Grating it from a block gives the smoothest melt; pre-grated cheese tends to be less silky in a cream sauce.
• Panko breadcrumbs — Their larger, airy flakes make a crisp topping rather than a fine, compact crust. Tossing them with olive oil helps them brown evenly across the casserole.
• Cooked leftover turkey and peas — Bite-size turkey pieces distribute through the sauce without requiring extra cooking, and frozen peas can go straight into the mixture. Use turkey that’s already cooked; raw turkey won’t work in this assembly method.

How to Build the Sauce Before the Casserole Goes in the Oven

Stop the Spaghetti Before It’s Fully Al Dente

Heat the oven to 375°F and grease a 9×13-inch baking dish. Bring a large pot of water to a boil, add 2 teaspoons of the measured kosher salt, and cook the spaghetti for two minutes less than the package timing for al dente. Drain it once the strands are pliable but still have a little firmness in the center. They’ll soften further as they bake in the sauce.

Brown the Mushrooms Until the Skillet Looks Dry

Melt the butter in a 12-inch skillet over medium heat, then add the sliced mushrooms and chopped onion. Cook for 7–9 minutes, stirring occasionally, until the mushrooms are browned, their liquid has evaporated, and the onion is tender. If the pan still has visible mushroom liquid, keep cooking before adding the flour; that moisture can thin the sauce later. Stir in the garlic and cook for 30 seconds.

Thicken the Cream Sauce, Then Coat the Turkey

Sprinkle the flour over the vegetables and cook, stirring, for 1 minute. Gradually whisk in the broth and heavy cream so the flour blends in smoothly, then bring the sauce to a simmer. Cook for 3–5 minutes, whisking often, until it thickens; stir in the remaining 1 teaspoon salt and the black pepper. Add the turkey, frozen peas, and Parmesan, stirring until the cheese melts and everything is coated.

Top the Casserole and Bake Until Bubbling

Combine the drained spaghetti and sauce in a large bowl, then transfer the mixture to the prepared baking dish. Toss the panko with olive oil and scatter it evenly over the top; an even layer gives you crunch from edge to edge. Bake for 25–30 minutes, until the topping is golden, the casserole bubbles at the edges, and the center reaches 165°F. Rest the casserole for 10 minutes before serving.

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Creamy Leftover Turkey Tetrazzini with Mushrooms

Leftover turkey tetrazzini combines spaghetti, mushrooms, turkey, peas, and Parmesan in a creamy sauce beneath a crisp panko topping. Baked until golden and bubbling, it rests for 10 minutes before serving.

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Prep Time 20 minutes mins

Cook Time 45 minutes mins

Resting 10 minutes mins

Total Time 1 hour hr 15 minutes mins

Servings: 8 servings

Course: Dinner

Cuisine: American

Calories: 535

Ingredients Equipment Method Notes

Ingredients

  

For the tetrazzini

• 12 oz spaghetti
• 1 tbsp kosher salt divided
• 4 tbsp unsalted butter
• 8 oz cremini mushrooms sliced
• 1 yellow onion medium, finely chopped
• 2 cloves garlic minced
• 0.25 cup all-purpose flour
• 2 cups low-sodium chicken broth
• 1 cup heavy cream
• 0.5 tsp black pepper
• 3 cups cooked leftover turkey cut into bite-size pieces
• 1 cup frozen peas
• 1 cup Parmesan cheese freshly grated

For the topping

• 1 cup panko breadcrumbs
• 1 tbsp olive oil

Equipment

• 1 9x13-inch baking dish
• 1 12-inch skillet

Method

 

1. Heat the oven to 375°F.
2. Grease a 9x13-inch baking dish.
3. Bring a large pot of water to a boil, add 2 teaspoons of the measured salt, and cook the spaghetti for 2 minutes less than the package directions for al dente; drain.

Make the sauce

1. Melt the butter in a 12-inch skillet over medium heat, add the mushrooms and onion, and cook for 7–9 minutes, stirring occasionally, until the mushrooms are browned and their liquid has evaporated and the onion is tender.
2. Stir in the garlic and cook for 30 seconds.
3. Sprinkle in the flour and cook, stirring, for 1 minute.
4. Gradually whisk in the broth and heavy cream, bring to a simmer, and cook for 3–5 minutes, whisking often, until the sauce thickens; stir in the remaining 1 teaspoon salt and the black pepper.
5. Stir in the turkey, peas, and Parmesan until the cheese melts and the turkey and peas are coated in sauce.

Assemble and bake

1. Combine the drained spaghetti and sauce in a large bowl, then transfer the mixture to the prepared baking dish.
2. Toss the panko with the olive oil and scatter it evenly over the casserole.
3. Bake for 25–30 minutes, until the topping is golden and the casserole is bubbling at the edges and reaches 165°F in the center.
4. Rest for 10 minutes before serving.

Notes

For the best texture, cook the spaghetti 2 minutes less than the package directions because it continues cooking in the oven. Refrigerate leftovers for 3–4 days; freeze for up to 3 months. For a gluten-free version, use gluten-free spaghetti, flour, and panko.