Butterfly the chicken breast and then, using a meat mallet, gently flatten the fillet to about 5mm
Season the surface with pepper and a sprinkle of Parmesan cheese (I do not use salt as the ham imparts enough saltiness)
Arrange 2 or 3 sage leaves on the surface
Cover with a slice of ham and secure the ham with 2 to 3 cocktail sticks
Heat the butter (or butter and oil mixture) and gently place the meat side down first. Fry for 60-90 seconds then turn gently and cook for a further 60 seconds. Remove and keep it warm, add the extra sage leaves and a little more butter if necessary, as you fry the sage leaves add the sherry and a squeeze of lemon juice. Pour this over the fried meat and serve immediately.