Preheat oven to 350°F.
Butterfly the chicken breasts by cutting a slit horizontally through each piece—don’t cut all the way—and opening it up. Season them with salt and pepper, and place 1/4 of the cheese in the center of each breast. Close the flap and then wrap each breast with a slice of prosciutto.
Remove the lemon from pan. Add a bit more oil, a turn of the pan, and wilt in spinach or kale; season with salt and pepper. Place greens on plate, top with chicken and douse everything with lemon juice.