Baked Chicken Tetrazzini with Mushrooms and Peas

Why You’ll Love This Recipe

• Classic comfort: creamy sherry–Parmesan sauce hugs every strand of spaghetti.
• Textural contrast: tender chicken and peas under a crisp, buttery panko crust.
• Weeknight-friendly: smart shortcuts like rotisserie chicken and frozen peas.
• Crowd-pleasing bake that’s perfect for potlucks, make-ahead dinners, or cozy weekends.

Grocery List

• Produce: Cremini mushrooms, yellow onion, garlic, flat-leaf parsley, lemon, frozen peas
• Dairy: Unsalted butter, whole milk, heavy cream, Parmesan cheese
• Pantry: Spaghetti, cooked chicken (rotisserie or poached), chicken broth, dry sherry, Dijon mustard, panko breadcrumbs, all-purpose flour, olive oil, kosher salt, black pepper, ground nutmeg

Full Ingredients

Pasta & Chicken

• 12 oz (340 g) dry spaghetti
• 4 cups cooked chicken, shredded or chopped (about 1 lb 4 oz / 565 g)

Sherry–Parmesan Cream Sauce

• 10 oz (285 g) cremini mushrooms, sliced 1/4 inch
• 1 tbsp olive oil
• 4 tbsp (56 g) unsalted butter
• 1 small yellow onion, finely chopped (about 1 cup / 140 g)
• 3 garlic cloves, minced
• 1/2 cup (120 ml) dry sherry (do not use “cooking sherry”)
• 1/3 cup (43 g) all-purpose flour
• 3 cups (720 ml) low-sodium chicken broth
• 1 cup (240 ml) whole milk
• 1 cup (240 ml) heavy cream
• 1.5 cups (about 3 oz / 85 g) finely grated Parmesan cheese
• 1 tsp Dijon mustard
• 1 tbsp fresh lemon juice
• 1/4 tsp ground nutmeg
• 1 cup (140 g) frozen peas
• 1.5–2 tsp kosher salt, to taste
• 3/4 tsp freshly ground black pepper

Buttery Breadcrumb Topping

• 1.5 cups (75 g) panko breadcrumbs
• 2 tbsp (28 g) unsalted butter, melted
• 1/2 cup (about 1 oz / 28 g) finely grated Parmesan cheese
• 2 tbsp finely chopped flat-leaf parsley
• Pinch of kosher salt

To Finish

• Additional chopped parsley for garnish (optional)

Step-by-Step Instructions

Step 1: Preheat and prep

Heat oven to 375°F (190°C). Lightly grease a 9×13-inch (3-quart) baking dish. Bring a large pot of well-salted water to a boil (about 1 tablespoon salt per 4 quarts water). Set a colander in the sink. Have a 1/2-cup measuring cup ready to reserve pasta water.

Step 2: Cook pasta very al dente

Add spaghetti and cook until very al dente, 2 minutes shy of package instructions (it will finish in the oven). Reserve 1/2 cup pasta water, then drain and set aside.

Step 3: Brown mushrooms and aromatics

Meanwhile, heat olive oil and 1 tablespoon of the butter in a large, deep skillet or Dutch oven over medium-high heat. Add mushrooms and a pinch of salt; cook, stirring occasionally, until they release moisture and turn golden brown at the edges, 6–8 minutes. Reduce heat to medium, add onion, and cook until translucent, 3–4 minutes. Stir in garlic and cook 30 seconds until fragrant.

Step 4: Deglaze with sherry and build the roux

Pour in the dry sherry and scrape up any browned bits. Simmer until reduced by about half, 1–2 minutes. Add the remaining 3 tablespoons butter. When melted, sprinkle flour evenly over the pan and stir for 1 minute to cook off the raw taste.

Step 5: Make the creamy sauce

Gradually whisk in the chicken broth, then the milk and cream. Bring to a gentle simmer, whisking often, until the sauce thickens enough to coat the back of a spoon, 5–7 minutes. Stir in Dijon, nutmeg, 1.5 cups Parmesan, lemon juice, peas, 1.5 teaspoons kosher salt, and the black pepper. Taste and add more salt if needed. The sauce should be slightly looser than you want in the final dish; it will thicken in the oven. If it seems too thick, whisk in a splash of pasta water.

Step 6: Combine with chicken and pasta

Add the shredded chicken and drained spaghetti to the sauce, tossing to coat. If needed, loosen with additional reserved pasta water 1–2 tablespoons at a time until creamy and glossy. Transfer the mixture to the prepared baking dish, spreading evenly.

Step 7: Top and bake

In a bowl, combine panko, melted butter, 1/2 cup Parmesan, parsley, and a pinch of salt. Sprinkle evenly over the casserole. Bake until the edges bubble and the top is golden, 20–25 minutes. For extra color, broil 1–2 minutes, watching closely. Let rest 10 minutes before serving. Garnish with more parsley if you like.

Pro Tips

• Undercook the pasta: stopping 2 minutes early prevents mushy noodles after baking.
• Reduce the sherry: simmering for a minute or two concentrates flavor and cooks off harsh alcohol notes.
• Sauce consistency matters: aim for slightly loose before baking; it thickens as it bakes and rests.
• Use freshly grated Parmesan for the best melt, flavor, and even browning in the topping.
• Rotisserie shortcut: pull the chicken while warm for easy shredding and juicy pieces.

Variations

• Turkey Tetrazzini: swap in leftover roasted turkey for the chicken, 1:1.
• No-sherry option: use 1/2 cup extra broth plus an extra 1–2 teaspoons lemon juice for brightness.
• Cheesy twist: replace 1/2 cup Parmesan in the sauce with shredded Gruyère or Swiss for a nuttier profile.
• Gluten-free: use GF spaghetti, GF panko, and thicken with 1:1 sweet rice flour or a cornstarch slurry.

Storage & Make-Ahead

Refrigerate leftovers, tightly covered, for up to 4 days. Reheat covered at 325°F (165°C) for 20–25 minutes; add a splash of milk or broth to keep it creamy. To assemble ahead, build the casserole (through Step 6), cover, and refrigerate up to 24 hours. Add 1/4 cup extra broth before topping and baking; bake 30–35 minutes from cold. To freeze, assemble without baking and skip the topping; wrap well and freeze up to 2 months. Thaw overnight, stir in a splash of broth if needed, add topping, and bake 35–45 minutes at 375°F (190°C) until hot and bubbly.

Nutrition (per serving)

Approximate for 1 of 8 servings: 630 calories; 39 g protein; 61 g carbohydrates; 31 g fat; 4 g fiber; 980 mg sodium. Values will vary based on brands and exact measurements.