Preheat Oven: 350°F (175°C). Grease a 9x13-inch baking dish.
Cook Pasta: Boil spaghetti according to package instructions. Drain and set aside.
Sauté Mushrooms: In a skillet, melt 2 tbsp butter over medium heat. Add mushrooms and cook until tender (5 mins). Remove and set aside.
Make Sauce: In the same skillet, melt remaining 2 tbsp butter. Whisk in flour to form a roux (1–2 mins). Gradually add chicken broth and cream, whisking until smooth. Stir in Parmesan, garlic powder, onion powder, salt, and pepper. Simmer until thickened (5 mins).
Combine Ingredients: In a large bowl, mix cooked spaghetti, shredded chicken, mushrooms, and sauce. Transfer to the baking dish.
Top with Cheese: Sprinkle cheddar cheese evenly over the top and dust with paprika.
Bake: 25–30 mins until bubbly and golden.
Rest: Let cool 5 mins before serving.
