This ChickenTetrazzini is the epitome of comfort food, with a creamy, irresistible cheese sauce coating seasoned rotisserie chicken and tender spaghetti.
PREP: Preheat oven to 325°F. Measure & set out half & 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.
ONION & GARLIC: Melt 4 tbsp butter in a large pot over high heat. Sauté onion and garlic for 5 minutes until golden.
SAUCE: 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 (~30 seconds). Pour in chicken broth, remaining half-and-half, and seasonings. Season with salt (start with 3/4 tsp) & pepper (start with 1/2 tsp). Continue cooking, stirring occasionally, until sauce thickens enough to leave a tract on a spoon (Note 3).
BAKE: 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 (Note 4). Transfer to baking dish, top with remaining cheese and optional breadcrumb topping (Note 2). Bake for 20-25 minutes until cheese is bubbly and golden. Garnish with fresh thyme if desired.
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.