Bring a large pot of salted water to a boil over high heat. Add spaghetti and cook according to package instructions until al dente, usually about 8-10 minutes. Drain the pasta in a colander and set aside.

In a large skillet, heat olive oil over medium-high heat. Season chicken breasts with salt, pepper, and paprika. Cook for 5–7 minutes on each side until golden brown and cooked through, reaching an internal temperature of 165°F. Remove chicken from skillet and let rest before slicing.

In the same skillet, reduce heat to medium and add unsalted butter. Once melted, add finely chopped yellow onion and sauté for 3–4 minutes until softened. Stir in minced garlic and cook for an additional 30 seconds.

Pour in chicken broth and heavy cream into the skillet, stirring well to combine. Bring to a gentle simmer over medium heat, allowing it to cook for about 5 minutes until slightly thickened.

Slice the seared chicken into bite-sized pieces and return to the skillet along with the cooked spaghetti. Toss everything together gently to coat.

Evenly sprinkle shredded Monterey Jack cheese over the pasta. Cover with a lid and let it sit on low heat for about 2-3 minutes, or until cheese melts.

Remove from heat and garnish with freshly chopped parsley. Serve hot.