Turkey tetrazzini casserole bakes leftover turkey with pasta in a creamy Parmesan sauce for a satisfying family dinner. This protein-rich dish is the best reason to look forward to Thanksgiving leftovers.
Preheat your oven to 375°F (190°C) and grease a 9x13 inch casserole dish for even baking.
Cook the spaghetti in salted, boiling water until just al dente, about 8 minutes, then drain and set aside.
Melt butter in a large skillet over medium heat, sauté chopped onion and sliced mushrooms for 5–7 minutes until softened and golden.
Stir in flour and cook for 1 minute, then gradually whisk in milk and chicken broth, adding cheese and seasoning for a creamy, thick sauce.
Combine cooked turkey, peas, pasta, and sauce in a large bowl. Toss well, then transfer to the casserole dish. Spread evenly and top with extra Parmesan if desired.
Bake uncovered for 25–30 minutes, until bubbling and golden brown at the edges. Let it rest for 5 minutes before serving for best texture.