In a large pot, bring salted water to a rolling boil over medium-high heat. Add the spaghetti and cook according to package instructions until al dente, about 8-10 minutes. Once cooked, drain the pasta thoroughly and set aside.

Heat a tablespoon of olive oil in a large skillet over medium heat. Season the chicken breasts with paprika, Italian seasoning, salt, and black pepper. Add the seasoned chicken to the skillet, searing for about 5-7 minutes on each side until golden and cooked through. Remove and set aside.

In the same skillet, melt 2 tablespoons of butter over medium heat. Add finely chopped onion and sauté for 3-4 minutes until translucent. Stir in minced garlic and cook for 30 seconds without burning.

Pour in 1 cup of chicken broth and 1 cup of heavy cream, stirring to combine. Allow to simmer on low for about 5 minutes, letting it thicken slightly.

Add the drained spaghetti and sliced seared chicken back to the skillet. Toss everything gently together until well-coated in the sauce. Heat for another 2-3 minutes.

Sprinkle 1-2 cups of shredded Monterey Jack cheese over the pasta mixture. Cover the skillet and reduce heat to low, allowing the cheese to melt for about 2-3 minutes.

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