**Cook the Spaghetti:**
- Bring a large pot of salted water to a boil and cook the spaghetti according to package instructions. Drain and set aside.
**Prepare the Chicken:**
- Heat olive oil in a medium skillet over medium heat. Add the shredded chicken, garlic powder, onion powder, smoked paprika, salt, and pepper. Toss to coat and cook for 2–3 minutes to enhance the flavor. Set aside.
**Make the Sauce:**
- In the same pot used for the spaghetti, melt the butter over medium heat. Add the minced garlic and sauté for 1 minute until fragrant.
- Whisk in the chicken broth, heavy cream, and sour cream. Cook until the mixture is slightly thickened, about 3–5 minutes.
- Stir in the Monterey Jack cheese, cheddar cheese, Parmesan cheese, Italian seasoning, and red pepper flakes (if using). Whisk until the cheese is fully melted and the sauce is smooth.
**Combine:**
- Add the cooked spaghetti and seasoned chicken to the sauce. Toss until everything is evenly coated.
**Assemble and Bake:**
- Preheat the oven to 375°F (190°C).
- Transfer the spaghetti mixture to a greased 9x13-inch baking dish. Sprinkle the top with crispy fried onions or panko breadcrumbs, if desired.
- Bake for 20–25 minutes, or until bubbly and golden on top.
**Serve:**
- Garnish with chopped parsley or green onions before serving. Enjoy warm!