This Chicken Tetrazzini Recipe is amazing comfort food, with a creamy, irresistible cheese sauce coating seasoned rotisserie chicken and tender spaghetti. Shop the recipe here.
Preheat oven to 325°F. Measure and set out half-and-half to get it to room temp. Grease a 9x13-inch ceramic baking dish. Bring 12 cups of water to a boil. Add 1 tbsp salt, cook broken spaghetti for 1 minute less than package instructions, drain, and set aside.
Melt the butter in a large pot over high heat. Sauté onion and garlic for 5 minutes until golden.
Reduce heat to medium. Sprinkle flour on top; stir constantly for 1 minute. Gradually add 1-1/2 cups half-and-half, stirring until thickened (about 30 seconds). Pour in chicken broth, remaining half-and-half, and seasonings. Season with salt (start with 3/4 tsp) and pepper (start with 1/2 tsp). Continue cooking, stirring occasionally, until sauce thickens enough to leave a tract on a spoon (see note 3).
Off heat, stir in half the cheese (no need to fully melt). Add pasta, chicken, and peas; mix until coated. Taste and adjust seasoning if needed (see note 4). Transfer to baking dish, top with remaining cheese and optional breadcrumb topping (see note 2). Bake for 20–25 minutes until cheese is bubbly and golden. Garnish with fresh thyme if desired.
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Notes
Note 1: Half-and-half is a blend of equal parts whole milk and cream. Substitute with half whole milk and half heavy cream if necessary.Note 2: For the breadcrumb topping, either brown panko in butter on the stovetop in a skillet with 1/4 teaspoon salt or mix panko with melted butter (microwave) and salt, then sprinkle over casserole before baking.Note 3: Sauce thickness should leave a trail (doesn’t rush to fill in the space). Whisk constantly to avoid flour settling and ensure even thickening. Doesn’t need to be ultra thick—sauce will thicken further upon adding pasta and chicken.Note 4: For extra flavor, especially if using less seasoned chicken, try adding chicken bouillon powder (starting with 1/2 tsp at a time) to taste.Storage: Let cool and store in the fridge in an airtight container for 3–5 days. If you plan to have leftovers, only add panko topping to what you’ll be eating. To freeze, assemble without panko topping, freeze up to 3 months, thaw overnight, and bake with extra 10–15 minutes.