Creamy Chicken Tetrazzini Casserole With Mushrooms and Cheese

Quick Recipe Version (TL;DR)

• Yield: 6 servings
• Prep Time: 25 minutes
• Cook Time: 40 minutes
• Total Time: 1 hour 5 minutes

Quick Ingredients

• 12 oz dry spaghetti or linguine
• 3 cups cooked shredded chicken (rotisserie or poached)
• 8 oz cremini or white mushrooms, sliced
• 1 small yellow onion, finely diced
• 3 cloves garlic, minced
• 4 Tbsp unsalted butter
• 1/4 cup all-purpose flour
• 2 cups low-sodium chicken broth
• 1 cup whole milk
• 1/2 cup heavy cream
• 4 oz cream cheese, softened and cubed
• 1 cup frozen peas, thawed
• 1/2 tsp dried thyme or Italian seasoning
• 1/4 tsp ground nutmeg
• 1 3/4 tsp kosher salt (divided, plus more for pasta water)
• 1/2 tsp freshly ground black pepper
• 1 1/2 cups shredded mozzarella cheese (divided)
• 1 cup freshly grated Parmesan cheese (divided)
• 2 Tbsp unsalted butter, cut into small pieces (for topping, optional)
• Chopped fresh parsley, for garnish (optional)

Do This

• 1. Preheat oven to 375°F (190°C). Grease a 9×13-inch baking dish or large oven-safe skillet. Bring a large pot of salted water to a boil.
• 2. Cook pasta until just shy of al dente (1–2 minutes less than package directions). Drain and set aside.
• 3. In a large skillet, sauté mushrooms and onion in 4 Tbsp butter over medium-high heat until softened and lightly browned; add garlic and cook 30 seconds.
• 4. Sprinkle in flour and cook 1 minute. Slowly whisk in broth, milk, and cream. Simmer until thickened, then whisk in cream cheese, 1/2 cup Parmesan, thyme, nutmeg, salt, and pepper.
• 5. Stir in chicken, peas, and cooked pasta until everything is well coated. Adjust seasoning to taste, then transfer mixture to the prepared baking dish if needed.
• 6. Top with remaining mozzarella and Parmesan; dot with 2 Tbsp butter if using. Bake 20–25 minutes, until bubbly and cheese is melted and golden at the edges.
• 7. Let rest 5–10 minutes. Garnish with chopped parsley, scoop into bowls, and serve hot.

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Why You’ll Love This Recipe

• Ultra-creamy, comforting casserole loaded with tender chicken, pasta, and mushrooms.
• Golden, bubbly cheese crust that bakes up beautifully in the oven.
• Uses pantry and grocery-store staples; easy enough for a weeknight but special enough for guests.
• Great make-ahead and freezer-friendly dish for busy days or bringing to friends and family.

Grocery List

• Produce: 1 small yellow onion, 3 cloves garlic, 8 oz cremini or white mushrooms, fresh parsley (optional)
• Dairy: Unsalted butter, whole milk, heavy cream, cream cheese, shredded mozzarella cheese, Parmesan cheese
• Pantry: Dry spaghetti or linguine, low-sodium chicken broth, all-purpose flour, frozen peas, dried thyme or Italian seasoning, ground nutmeg, kosher salt, black pepper, cooking spray or oil for greasing

Full Ingredients

Pasta & Chicken

• 12 oz dry spaghetti or linguine
• 3 cups cooked shredded chicken (about 1 to 1 1/4 lb cooked; rotisserie works perfectly)
• Kosher salt, for pasta water

Vegetables & Aromatics

• 8 oz cremini or white mushrooms, cleaned and thinly sliced
• 1 small yellow onion, finely diced (about 1 cup)
• 3 cloves garlic, minced

Creamy Sauce

• 4 Tbsp unsalted butter
• 1/4 cup all-purpose flour
• 2 cups low-sodium chicken broth
• 1 cup whole milk
• 1/2 cup heavy cream
• 4 oz cream cheese, softened and cut into small cubes
• 1/2 cup freshly grated Parmesan cheese
• 1/2 tsp dried thyme or Italian seasoning
• 1/4 tsp ground nutmeg
• 1 1/4 tsp kosher salt (plus more to taste)
• 1/2 tsp freshly ground black pepper (plus more to taste)
• 1 cup frozen peas, thawed

Cheesy Topping

• 1 cup shredded mozzarella cheese
• 1/2 cup freshly grated Parmesan cheese
• 2 Tbsp unsalted butter, cut into small pieces (optional, for extra browning and richness)

Optional Garnish

• 2–3 Tbsp chopped fresh parsley

Step-by-Step Instructions

Step 1: Preheat and Prepare Your Baking Dish

Preheat your oven to 375°F (190°C). Grease a 9×13-inch baking dish or a large, deep oven-safe skillet (such as cast iron) with butter, oil, or nonstick spray. This will prevent the creamy sauce and cheese from sticking and help the edges brown nicely. Set the dish aside near your stove so it is ready when the filling is done.

Step 2: Cook the Pasta Until Just Shy of Al Dente

Bring a large pot of well-salted water to a boil (about 1–2 Tbsp kosher salt for a big pot). Add the 12 oz of pasta and cook until just shy of al dente, usually 1–2 minutes less than the package instructions. The pasta will soften further as it bakes, so undercooking slightly helps prevent mushiness. Drain the pasta well and set aside. If you are worried it may stick together, toss it with a teaspoon of olive oil.

Step 3: Sauté Mushrooms, Onion, and Garlic

While the pasta cooks, place a large deep skillet or sauté pan over medium-high heat. Add 4 Tbsp unsalted butter. Once melted and foamy, add the sliced mushrooms and diced onion. Cook, stirring occasionally, for 6–8 minutes, until the mushrooms have released their moisture and are lightly browned and the onions are soft and translucent. Reduce the heat to medium, add the minced garlic, and cook for 30–60 seconds, just until fragrant. Do not let the garlic burn.

Step 4: Build the Creamy Sauce

Sprinkle the 1/4 cup flour evenly over the mushroom mixture. Stir constantly for about 1 minute to coat the vegetables and cook off the raw flour taste. Slowly pour in the 2 cups chicken broth while whisking or stirring vigorously to avoid lumps. Once incorporated, add the 1 cup milk and 1/2 cup heavy cream in a steady stream, continuing to whisk. Bring the mixture to a gentle simmer; it should start to thicken in 3–5 minutes.

Reduce the heat to low. Stir in the cubed cream cheese, whisking until fully melted and the sauce is smooth. Add 1/2 cup grated Parmesan, 1/2 tsp dried thyme or Italian seasoning, 1/4 tsp nutmeg, 1 1/4 tsp kosher salt, and 1/2 tsp black pepper. Taste and adjust seasoning with additional salt and pepper if needed. The sauce should be luxuriously thick and well-seasoned at this point.

Step 5: Add Chicken, Peas, and Pasta

Stir the 3 cups of shredded chicken and 1 cup thawed peas into the hot sauce, folding gently to coat everything evenly. Add the cooked, drained pasta to the pan, using tongs or a large spoon to toss until each strand is coated with the creamy mixture and the chicken and vegetables are well distributed. If your skillet is not oven-safe or not large enough, transfer everything into the greased 9×13-inch baking dish now, spreading it into an even layer.

Step 6: Top with Cheese and Bake Until Golden

In a small bowl, combine 1 cup shredded mozzarella and 1/2 cup grated Parmesan. Sprinkle this cheese mixture evenly over the top of the pasta. If you like an extra-rich, slightly crisp top, dot the surface with the 2 Tbsp butter pieces. Place the baking dish on the center rack of the preheated oven.

Bake for 20–25 minutes, or until the casserole is bubbling around the edges and the cheese is fully melted and lightly golden. If you prefer a deeper golden-brown crust, switch the oven to broil for 1–3 minutes at the end, watching carefully so it does not burn.

Step 7: Rest, Garnish, and Serve

Remove the casserole from the oven and let it rest for 5–10 minutes. This short resting time allows the sauce to thicken slightly so the servings hold together better. Sprinkle with chopped fresh parsley for a bit of color and freshness if desired. Scoop generous portions into warm bowls or plates and serve hot, making sure each serving gets plenty of chicken, mushrooms, and that cheesy top layer.

Pro Tips

• Do not overcook the pasta: Slightly undercooking the pasta before baking is key to avoiding a mushy casserole. Aim for just shy of al dente.
• Season the sauce generously: The pasta and chicken will dilute the flavors, so be sure to taste and adjust the sauce before adding them. A pinch more salt or pepper can make a big difference.
• Use freshly grated cheese: Freshly grated Parmesan and mozzarella melt more smoothly and create a better golden crust than pre-shredded cheese, which often contains anti-caking agents.
• Make it in one pan: If you have a large, deep, oven-safe skillet (like a 12-inch cast iron), you can build the sauce, combine everything, and bake in the same pan for easier cleanup.
• Add a crunchy element (if you like): For a slightly crunchy topping, mix 1/2 cup panko breadcrumbs with 1 Tbsp melted butter and sprinkle over the cheese before baking.

Variations

• Turkey Tetrazzini: Swap the chicken for leftover roasted or smoked turkey for a fantastic post-holiday casserole.
• Veggie-Loaded: Add 1 cup of steamed broccoli florets or sautéed spinach along with the peas for extra vegetables and color.
• Mushroom Lovers: Use a mix of cremini, shiitake, and button mushrooms and increase the total amount to 12 oz for a deeper, earthier flavor.

Storage & Make-Ahead

Allow the baked tetrazzini to cool to room temperature. Cover tightly and refrigerate for up to 3 days. Reheat individual portions in the microwave or rewarm the entire dish in a 350°F (175°C) oven, covered with foil, for 20–25 minutes or until hot in the center. For make-ahead, assemble the casserole through the cheese-topping step, cover tightly, and refrigerate up to 24 hours. When ready to bake, let it sit at room temperature for 20–30 minutes, then bake as directed, adding 5–10 extra minutes if needed. To freeze, wrap the unbaked casserole very well (plastic wrap plus foil) and freeze for up to 2 months. Thaw overnight in the refrigerator before baking.

Nutrition (per serving)

Approximate values per serving (1/6 of recipe): about 650–700 calories, 34–38 g protein, 30–35 g fat, 50–55 g carbohydrates, 3–4 g fiber, and 900–1000 mg sodium. These numbers will vary based on the specific brands of ingredients and exact amounts used.