Step 1: Prepare the Chicken

1. If using raw chicken, heat 1 tablespoon of olive oil in a skillet over medium heat. Season the chicken breasts or thighs with smoked paprika, garlic powder, onion powder, salt, and black pepper.
2. Cook the chicken for 6-7 minutes per side, or until fully cooked and no longer pink in the center. Let it rest for 5 minutes before shredding with two forks. Set aside.

Step 2: Cook the Spaghetti

1. Bring a large pot of salted water to a boil. Add the spaghetti and cook until al dente according to package instructions. Reserve ½ cup of pasta water, then drain and set aside.

Step 3: Make the Sauce

1. In a large skillet or saucepan, melt the butter over medium heat. Add the diced onion and bell peppers, sautéing for 3-4 minutes until softened.
2. Stir in the minced garlic and cook for an additional 30 seconds until fragrant.
3. Sprinkle the flour over the vegetables and cook for 1-2 minutes, stirring constantly, to create a roux.
4. Gradually whisk in the chicken broth and heavy cream, ensuring the mixture is smooth and lump-free. Bring to a gentle simmer and cook for 2-3 minutes until slightly thickened.
5. Reduce the heat to low and stir in the shredded Monterey Jack cheese and cheddar cheese until melted and smooth. Add smoked paprika, onion powder, salt, and black pepper. Taste and adjust seasonings as needed.

Step 4: Assemble the Casserole

1. Preheat your oven to 375°F (190°C).
2. In a large mixing bowl, combine the cooked spaghetti, shredded chicken, crumbled bacon, and the creamy cheese sauce. Toss everything together until evenly coated. If the mixture seems too thick, add a splash of reserved pasta water to loosen it.
3. Transfer the mixture to a greased 9×13-inch baking dish. Spread it out evenly and sprinkle the remaining 1 cup of shredded Monterey Jack cheese over the top.

Step 5: Bake the Casserole

1. Bake the casserole in the preheated oven for 20-25 minutes, or until the cheese is melted and bubbly. For a golden-brown top, broil for an additional 2-3 minutes, keeping a close eye to prevent burning.

Step 6: Garnish and Serve

1. Remove the casserole from the oven and let it rest for 5 minutes. Garnish with freshly chopped parsley, if desired.
2. Serve hot and enjoy your Monterey Chicken Spaghetti with a side of garlic bread or a fresh green salad.