Preheat oven to 350 degrees. Spray one 9×13 and one 9×9 glass dish with nonstick cooking spray and set aside.

In a large bowl, add spaghetti and butter and toss gently. Mix chicken and next 7 ingredients; toss gently. Combine flour and sherry in medium bowl, beating well with a wire whisk. Add broth, half and half, and garlic powder; stir well. Pour over spaghetti mixture; stir gently.

Spoon into baking dish. Sprinkle evenly with cheese, seasoned salt, almonds and breadcrumbs.

Bake at 350 degrees for 45 minutes. Cover with foil and bake an additional 10-12 minutes or until bubbly.

Version 2
Preheat oven to 425 degrees

In medium saucepan over medium heat, melt 1 T. butter and olive oil. Cook the mushrooms, onions, garlic and thyme until onions are tender, about 5 minutes. Remove and set aside

Melt remaining butter in the same pan. Add flour & whisk for 2 minutes. Whisk in milk, cream, broth, nutmeg and salt & pepper. Bring to a low boil and simmer until sauce thickens, 8-10 minutes, continue to whisk the entire time.

Meanwhile, bring a pot of salted water to a boil. Add the spaghetti and cook until tender but still al dente. Drain pasta well and return to pot. Add in veggies, chicken and sauce and mix well. Pour into a 9×13 baking dish.

Stir together the cheese and bread crumbs and sprinkle over the top. Bake uncovered until golden brown and bubbly, about 30 minutes.