Quick Recipe Version (TL;DR)
Quick Ingredients
- 12 oz dry spaghetti
- 3 cups cooked shredded roast chicken (about 1 lb)
- 12 oz cremini mushrooms, sliced
- 1 small yellow onion, finely chopped
- 3 garlic cloves, minced
- 1 cup frozen peas
- 4 tbsp unsalted butter (for sauce) + 1 tbsp olive oil
- 1/3 cup all-purpose flour
- 1/2 cup dry white wine (optional; or sub 1/2 cup broth)
- 2 cups low-sodium chicken broth
- 1 1/2 cups half-and-half + 1/2 cup heavy cream
- 1 cup finely grated Parmesan (plus 1/3 cup for topping)
- 1 tsp Dijon mustard (optional), pinch nutmeg
- 1 tsp fresh thyme (or 1/2 tsp dried), 2 tbsp chopped parsley
- 1 cup panko + 3 tbsp melted butter (for topping)
- Kosher salt, black pepper, 2 tsp lemon juice (optional)
Do This
- 1) Heat oven to 375°F (190°C). Butter a 9×13-inch baking dish.
- 2) Boil spaghetti in salted water until 1 minute shy of al dente; drain, reserve 1/2 cup pasta water.
- 3) Sauté mushrooms in 2 tbsp butter and 1 tbsp oil until browned; add onion, garlic, thyme.
- 4) Add 2 tbsp butter, sprinkle in flour; whisk in wine, broth, half-and-half, and cream. Simmer to thicken; stir in Parmesan, mustard, nutmeg, peas, parsley. Season.
- 5) Toss sauce with spaghetti and chicken; add a splash of pasta water if needed. Spread in dish.
- 6) Mix panko, 1/3 cup Parmesan, 3 tbsp melted butter, salt, pepper; scatter over top.
- 7) Bake 25 minutes until bubbly and golden; broil 1–2 minutes if needed. Rest 10 minutes, garnish, serve.
Why You’ll Love This Recipe
- Cozy comfort: creamy, cheesy sauce clings to every strand of spaghetti.
- Weeknight-friendly: uses rotisserie chicken and pantry staples.
- Great texture: tender pasta and chicken under a buttery, crisp panko lid.
- Make-ahead magic: assemble earlier, bake when you are ready.
Grocery List
- Produce: Cremini mushrooms, yellow onion, garlic, fresh thyme (or dried), parsley, lemon
- Dairy: Unsalted butter, half-and-half, heavy cream, Parmesan cheese
- Pantry: Dry spaghetti, low-sodium chicken broth, dry white wine (optional), all-purpose flour, panko breadcrumbs, olive oil, Dijon mustard, kosher salt, black pepper, nutmeg
Full Ingredients
Pasta and Chicken
- 12 oz dry spaghetti
- 3 cups cooked shredded roast chicken (about 1 lb)
- 1 cup frozen peas (no need to thaw)
Mushroom–Parmesan Cream Sauce
- 2 tbsp unsalted butter + 1 tbsp olive oil (for sautéing)
- 12 oz cremini or baby bella mushrooms, thinly sliced
- 1 small yellow onion, finely chopped (about 1 cup)
- 3 garlic cloves, minced
- 1 tsp fresh thyme leaves (or 1/2 tsp dried thyme)
- 2 tbsp unsalted butter (added before flour)
- 1/3 cup all-purpose flour
- 1/2 cup dry white wine (optional; or substitute 1/2 cup additional chicken broth)
- 2 cups low-sodium chicken broth
- 1 1/2 cups half-and-half
- 1/2 cup heavy cream
- 1 cup finely grated Parmesan cheese
- 1 tsp Dijon mustard (optional but recommended)
- 1/4 tsp ground nutmeg
- 1 tsp kosher salt, plus more to taste
- 1/2 tsp freshly ground black pepper
- 2 tbsp chopped fresh parsley
- 2 tsp fresh lemon juice (optional, to brighten)
Buttery Crumb Topping
- 1 cup panko breadcrumbs
- 3 tbsp unsalted butter, melted
- 1/3 cup finely grated Parmesan cheese
- Pinch kosher salt and black pepper
Step-by-Step Instructions
Step 1: Preheat and prep the dish
Heat the oven to 375°F (190°C). Grease a 9×13-inch baking dish with butter or nonstick spray. Set a large pot of well-salted water (1 tablespoon kosher salt per 4 quarts) over high heat for the pasta. Finely chop the onion, slice the mushrooms, mince the garlic, and chop the parsley. Shred the cooked chicken if not already done.
Step 2: Cook the spaghetti
Boil the spaghetti until just shy of al dente, usually 1 minute less than package directions (about 8–9 minutes). Reserve 1/2 cup of the starchy pasta water, then drain and set aside. Toss with a little olive oil if you like to prevent sticking.
Step 3: Sauté mushrooms and aromatics
In a large deep skillet or Dutch oven over medium-high heat, melt 2 tablespoons butter with 1 tablespoon olive oil. Add the sliced mushrooms and 1/2 teaspoon kosher salt. Cook, stirring occasionally, until the mushrooms release their moisture and are nicely browned, 7–9 minutes. Reduce heat to medium, add the onion, garlic, and thyme; cook until the onion is soft and translucent, 3–4 minutes.
Step 4: Build the Parmesan cream sauce
Add the remaining 2 tablespoons butter to the pan. Sprinkle in the flour and cook, stirring constantly, for 1 minute to form a roux. Whisk in the wine (if using) and cook until mostly absorbed, about 30 seconds. Gradually whisk in the chicken broth, then the half-and-half and heavy cream. Bring to a gentle simmer and cook until thick enough to coat the back of a spoon, 4–5 minutes. Stir in 1 cup Parmesan, Dijon, nutmeg, 1 teaspoon kosher salt, and 1/2 teaspoon pepper until smooth. Fold in the peas and parsley. Taste and brighten with lemon juice if desired. The sauce should be creamy but pourable; add a splash of reserved pasta water if it seems too thick.
Step 5: Combine pasta, chicken, and sauce
Add the drained spaghetti and shredded chicken to the sauce. Toss until every strand is coated and the chicken and peas are evenly distributed. If needed, loosen with more reserved pasta water so it remains slightly saucy (it will thicken in the oven).
Step 6: Transfer and add the buttery crumbs
Scrape the mixture into the prepared baking dish and smooth the top. In a bowl, combine the panko, 1/3 cup Parmesan, melted butter, a pinch of salt, and a few grinds of pepper. Sprinkle the crumbs evenly over the casserole.
Step 7: Bake, broil, and rest
Bake until the casserole is bubbling around the edges and the topping is golden, 25–28 minutes. For deeper color, broil 1–2 minutes, watching closely. Let rest 10 minutes before serving so the sauce can settle and cling to the spaghetti. Garnish with extra parsley and freshly cracked pepper.
Pro Tips
- Salt smartly: season at each stage (mushrooms, sauce, final taste) for layers of flavor without oversalting.
- Keep it saucy: make the sauce a touch looser than you think; pasta and baking thicken it.
- Brown the mushrooms well: good color means deeper, savory flavor in the final dish.
- Use freshly grated Parmesan: it melts smoothly and seasons the sauce better than pre-grated.
- Broil with caution: 30–60 seconds can take you from golden to too dark. Watch the topping closely.
Variations
- Turkey Tetrazzini: Swap the chicken for leftover roast turkey.
- Spinach-Mushroom: Fold in 4 cups baby spinach (wilt in the sauce) for extra greens.
- Gluten-Free: Use gluten-free spaghetti and gluten-free panko; thicken the sauce with a 1:1 gluten-free flour blend.
Storage & Make-Ahead
Assemble up to 24 hours ahead: cover and refrigerate. Bake covered at 375°F (190°C) for 20 minutes, then uncover and bake 15–20 minutes more until hot and golden. Leftovers keep 3–4 days in the refrigerator; reheat covered at 325°F (165°C) for 15–20 minutes, or microwave in portions. To freeze, assemble (unbaked), wrap tightly, and freeze up to 3 months. Bake from frozen, covered, at 350°F (175°C) for 45–55 minutes, then uncover and bake 10–15 minutes more to crisp the topping.
Nutrition (per serving)
Approximate: 730 calories; 43 g protein; 59 g carbohydrates; 36 g fat; 3 g fiber; 980 mg sodium. Values will vary based on brands and salt levels.
