Preheat oven to 425˚F. Coat the bottom of an oven-proof pan with 2 tablespoons of butter.
Place the chicken breasts on a cutting board and with a sharp knife cut a pocket into the side of each chicken breast, without cutting all the way through. Season each breast with garlic powder, paprika, salt, and pepper. Drizzle 2 tablespoons of olive oil all over the chicken breasts. Set aside.
In a mixing bowl, combine cream cheese, gruyere, parmesan, mayo, spinach, and garlic. Spread the spinach mixture evenly into each chicken breast. Thread 2 toothpicks on each breast to close the pocket and to prevent the filling from oozing out.
Place chicken on the prepared pan. Spread the remaining butter on top of the chicken breasts, and pour wine or broth into the bottom of the pan. Transfer to the oven and bake uncovered for 20-25 minutes, or until the internal temperature of the chicken registers at 165˚F.
Rest chicken for 5 minutes. Spoon pan juices over the chicken, squeeze fresh lemon juice, and top with fresh parsley. Serve immediately. Enjoy!
