Bring a large pot of salted water to a boil and add the spaghetti. Cook according to the package instructions, typically around 8–10 minutes, until al dente. Drain the pasta in a colander and set aside.

In a large skillet over medium heat, add 1 tablespoon of olive oil. Once the oil shimmers, add the chopped onion, bell peppers, and mushrooms. Sauté for 5-7 minutes until the veggies are softened and slightly caramelized.

Reduce the heat to low and add 1 can of cream of chicken soup and 1 cup of sour cream to the skillet. Sprinkle in the garlic powder and onion powder, then pour in ½ cup of milk. Stir thoroughly until the sauce is smooth and heated through.

Fold in 2 cups of shredded cooked chicken and half of the shredded Monterey Jack cheese into the creamy sauce mixture. Continue to cook until the cheese melts and the chicken is warmed through.

Carefully fold the cooked spaghetti into the creamy chicken mixture, ensuring that all the pasta is well coated with the delicious sauce.

If you prefer a baked version, preheat your oven to 350°F (175°C). Transfer the combined noodle mixture into a greased baking dish and top with the remaining Monterey Jack and cheddar cheese. Bake for 20-25 minutes until bubbling and golden brown on top.

Remove from the oven and let it cool slightly. Garnish with freshly chopped parsley before serving warm.