Cook pasta in a large pot of salted boiling water according to package instructions (8–10 minutes). Drain and set aside.

Heat olive oil in a large skillet over medium heat. Sauté chopped onion, bell pepper, and sliced mushrooms for 5–7 minutes until softened.

Lower heat, add cream of chicken soup, stir in sour cream, garlic powder, onion powder, and half a cup of milk. Cook for 2–3 minutes until heated through.

Fold in cooked chicken and half of the Monterey Jack cheese, stir constantly until cheese melts and mixture is heated.

Add drained spaghetti to the skillet, tossing to coat well with the creamy sauce. Stir for another minute until everything is evenly mixed.

For a baked version, preheat oven to 350°F (175°C), transfer pasta mixture to a greased baking dish and top with remaining Monterey Jack and cheddar cheeses. Bake for 20–25 minutes.

Once baked, let cool for a minute, garnish with parsley, and serve warm.