Bring a large pot of water to a boil, add salt, and cook spaghetti according to package instructions until al dente, about 8-10 minutes. Drain and set aside.

In a large skillet, heat olive oil over medium heat. Sauté chopped onion, bell pepper, and sliced mushrooms for 5-7 minutes until tender.

Incorporate cream of chicken soup and sour cream, stirring in garlic powder, onion powder, and milk until smooth. Cook for 3-4 minutes.

Fold in cooked chicken and half of the shredded Monterey Jack cheese, cooking for an additional 3-5 minutes until cheese melts.

Add drained spaghetti to the skillet, tossing gently until the pasta is well coated in the sauce.

(Optional) Transfer to a greased baking dish, sprinkle remaining cheese, and bake in a preheated oven at 350°F (175°C) for 20-25 minutes until bubbly.

Remove from oven, let cool slightly, garnish with parsley, and serve warm with garlic bread and salad.