Quick Recipe Version (TL;DR)
Quick Ingredients
- 12 oz (340 g) spaghetti
- 4 tbsp unsalted butter, plus 2 tbsp for topping
- 1 tbsp olive oil
- 1 medium yellow onion, finely diced
- 12 oz (340 g) cremini mushrooms, sliced
- 4 cloves garlic, minced
- 1/4 cup all-purpose flour
- 2 cups low-sodium chicken or turkey broth
- 1 1/2 cups whole milk
- 1/2 cup heavy cream
- 1 1/2 cups finely grated Parmesan, divided
- 3 cups cooked shredded turkey (or chicken)
- 1 cup frozen peas (no need to thaw)
- 1 tbsp lemon juice
- 1/4 cup chopped fresh parsley
- 1 1/2 cups shredded mozzarella
- 3/4 cup panko breadcrumbs
- Kosher salt, black pepper, pinch of nutmeg (optional)
Do This
- 1) Heat oven to 375°F. Butter a 9×13-inch baking dish.
- 2) Boil spaghetti in salted water until just shy of al dente; reserve 1 cup pasta water and drain.
- 3) Sauté onion + mushrooms in butter/olive oil; add garlic.
- 4) Stir in flour, then whisk in broth, milk, and cream; simmer until thick. Stir in Parmesan.
- 5) Toss sauce with spaghetti, turkey, peas, lemon juice, parsley; loosen with a splash of pasta water if needed.
- 6) Top with mozzarella and buttered panko-Parmesan crumbs.
- 7) Bake 18–22 minutes until bubbly and lightly browned; rest 10 minutes, then serve.
Why You’ll Love This Recipe
- Comfort-food classic: creamy mushroom-garlic sauce, tender turkey, and pasta in every bite.
- Perfect for leftovers: it’s one of the best ways to use cooked turkey or rotisserie chicken.
- Great texture: gooey mozzarella plus crunchy, buttery breadcrumbs on top.
- Freezer-friendly: bake now or assemble ahead for an easy future dinner.
Grocery List
- Produce: 1 medium yellow onion, 12 oz cremini mushrooms, 4 cloves garlic, 1 lemon, fresh parsley
- Dairy: unsalted butter, whole milk, heavy cream, Parmesan cheese, mozzarella cheese
- Protein: cooked shredded turkey (or chicken)
- Pantry: spaghetti, all-purpose flour, low-sodium chicken/turkey broth, frozen peas, panko breadcrumbs, kosher salt, black pepper, ground nutmeg (optional), olive oil
Full Ingredients
Pasta & Mix-Ins
- 12 oz (340 g) spaghetti
- 3 cups cooked shredded turkey (about 1 lb / 450 g cooked meat), or cooked shredded chicken
- 1 cup (140 g) frozen peas (no need to thaw)
- 1 tbsp lemon juice (from about 1/2 lemon)
- 1/4 cup (10 g) chopped fresh parsley, plus more for serving (optional)
Creamy Mushroom-Garlic-Parmesan Sauce
- 4 tbsp (56 g) unsalted butter
- 1 tbsp olive oil
- 1 medium yellow onion, finely diced (about 1 cup)
- 12 oz (340 g) cremini mushrooms, sliced
- 4 cloves garlic, minced
- 1/4 cup (32 g) all-purpose flour
- 2 cups (480 ml) low-sodium chicken or turkey broth
- 1 1/2 cups (360 ml) whole milk
- 1/2 cup (120 ml) heavy cream
- 1 1/2 cups (150 g) finely grated Parmesan cheese, divided (1 1/4 cups for sauce, 1/4 cup for topping)
- 1 1/2 tsp kosher salt, plus more for pasta water (adjust to taste)
- 1/2 tsp freshly ground black pepper
- 1/8 tsp ground nutmeg (optional, but excellent in creamy sauces)
Topping
- 1 1/2 cups (150 g) shredded mozzarella cheese
- 3/4 cup (45 g) panko breadcrumbs
- 2 tbsp (28 g) unsalted butter, melted
- 2 tbsp (10 g) finely grated Parmesan cheese (from the divided Parmesan)
Optional (Nice for Serving)
- Extra chopped parsley
- Extra black pepper
Step-by-Step Instructions
Step 1: Prep the oven and baking dish
Arrange a rack in the middle of the oven and preheat to 375°F (190°C). Lightly butter a 9×13-inch baking dish (or similar 3-quart casserole dish) and set aside.
Step 2: Cook the spaghetti just shy of al dente
Bring a large pot of water to a boil. Add 1 tablespoon kosher salt to the water (this is key for flavorful pasta). Add the 12 oz spaghetti and cook for 2 minutes less than the package directions, so it stays slightly firm.
Before draining, carefully reserve 1 cup (240 ml) pasta water. Drain the spaghetti and set aside.
Step 3: Sauté the mushrooms and onion
In a large, deep skillet or Dutch oven over medium-high heat, melt 4 tablespoons butter with 1 tablespoon olive oil. Add the diced onion and cook for 3 minutes, stirring occasionally, until it starts to soften.
Add the sliced mushrooms and cook for 7–9 minutes, stirring now and then, until the mushrooms release their liquid and the pan looks mostly dry. This helps concentrate the mushroom flavor instead of watering down your sauce.
Step 4: Add garlic, then build the creamy sauce
Add the minced garlic and cook for 30 seconds, just until fragrant (don’t let it brown).
Sprinkle in the 1/4 cup flour and stir constantly for 1 minute to cook off the raw flour taste. While stirring, slowly pour in the 2 cups broth. Once smooth, whisk in the 1 1/2 cups milk and 1/2 cup heavy cream.
Bring to a gentle simmer, then reduce heat to medium and cook for 3–5 minutes, stirring frequently, until the sauce thickens enough to coat a spoon. Season with 1 1/2 teaspoons kosher salt, 1/2 teaspoon black pepper, and 1/8 teaspoon nutmeg (if using).
Turn off the heat and stir in 1 1/4 cups (about 125 g) Parmesan until fully melted and silky.
Step 5: Combine pasta, turkey, peas, and finishing flavors
Add the drained spaghetti to the sauce and toss well. Add the 3 cups shredded turkey and 1 cup frozen peas, and stir until evenly distributed.
Stir in the 1 tablespoon lemon juice and 1/4 cup chopped parsley. If the mixture looks very thick (it can happen depending on your pasta shape and turkey moisture), stir in a splash of reserved pasta water, 1/4 cup at a time, until it looks creamy and spoonable (you may not need the full cup).
Step 6: Assemble and add the mozzarella + crunchy breadcrumb topping
Spoon the pasta mixture into the prepared baking dish and spread into an even layer.
Sprinkle 1 1/2 cups shredded mozzarella evenly over the top.
In a small bowl, combine 3/4 cup panko, 2 tablespoons melted butter, and the remaining 2 tablespoons Parmesan. Sprinkle the buttered crumbs evenly over the mozzarella.
Step 7: Bake until bubbly and lightly browned
Bake uncovered at 375°F (190°C) for 18–22 minutes, until the edges are bubbling and the top is lightly browned.
Let the casserole rest for 10 minutes before serving. This short rest helps the sauce set up so you get neat, creamy scoops instead of runny portions.
Pro Tips
- Undercook the pasta: Pull it about 2 minutes early so it finishes perfectly in the oven without going soft.
- Cook off mushroom moisture: Wait until the pan looks mostly dry before adding flour; it keeps the sauce rich and concentrated.
- Reserve pasta water on purpose: A few splashes make the sauce glossy and creamy again if it thickens while you assemble.
- Grate your own Parmesan if you can: Pre-grated cheese may not melt as smoothly. Finely grated Parmesan disappears into the sauce.
- Rest before serving: 10 minutes makes a big difference in texture and portioning.
Variations
- Chicken Tetrazzini: Swap turkey for 3 cups shredded rotisserie chicken (white or dark meat both work).
- Extra-veg version: Add 1 cup baby spinach (stir in at the end to wilt) or 1 cup chopped steamed broccoli.
- Cheesier top: Replace half the mozzarella with 3/4 cup shredded provolone for extra melt and flavor.
Storage & Make-Ahead
Refrigerate: Cool completely, then cover and refrigerate for up to 4 days.
Reheat: Cover with foil and bake at 350°F (175°C) for 20–25 minutes, or until heated through. For a crispier top, uncover for the last 5 minutes. You can also microwave individual portions for 2–3 minutes, stirring halfway through.
Make-ahead (best method): Assemble everything except the breadcrumb topping, cover, and refrigerate up to 24 hours. When ready to bake, add the buttered panko and bake at 375°F (190°C) for 25–30 minutes (the cold casserole takes a bit longer).
Freeze: Assemble in a freezer-safe dish, wrap tightly, and freeze for up to 2 months. Thaw overnight in the refrigerator, add topping if needed, then bake at 375°F (190°C) for 25–35 minutes until bubbly.
Nutrition (per serving)
Approximate, based on 8 servings: 560 calories, 33 g protein, 58 g carbohydrates, 22 g fat, 4 g fiber, 780 mg sodium.
