Lightly oil & heat a griddle pan or a frying pan, then grill the gammon for a couple of minutes on each side until lightly charred. Transfer to a plate and rest under cover.
Brush the pineapple slices with oil, then grill on both sides for a minute or so until lightly charred and caramelised.
Add the pineapple juice (about 2 Tbsp) to the pan and let it bubble until you get a thick sauce.
Scatter the salad leaves onto two plates, place the gammon on them, top with the pineapple then pour over the sauce.
Serve immediately.