Heat a nonstick pan over medium-low. Place the chicken breasts in the pan and cook for about 7 minutes on each side, depending on the size. The prosciutto should be browned, and your chicken cooked through. You can slice into the thickest point of the chicken and check for pink if you're nervous. Or, I recommend buying a little cake tester for checking the doneness of your meats. Insert the wire end of the cake tester to the thickest point, let it rest there for a few seconds. Then remove and hold it to the inside of your wrist. A bit tricky, but once you get the hang of it, a cake tester is the most reliable way to gauge doneness.