Preheat the broiler or grill.
Cut the top and bottom off the pineapple and, working vertically, slice the skin off the fruit. Cut into quarters and then into about three pieces again lengthwise so you have wedges of pineapple. Cut out the woody core and arrange the pineapple in a shallow dish.
Chop the chocolate and place it and the rum into a bowl over hot water. (Bring the water to a boil, then remove it from the heat and place the bowl of chocolate and rum on top.) Stir melted mixture thoroughly, then add the cream plus any juice that has gathered in the plate of fruit. When the sauce is thick, smooth and hot, pour into a bowl with a ladle, or enough little bowls to give one per person.
Thread the pineapple onto the skewers. Lay the pineapple kebabs on a sheet of foil and sprinkle them with brown sugar. Either broil or grill the pineapple until it caramelizes and scorches along the edges.
Take the kebabs from the broiler or grill and lay them on a large plate. Let guests take kebabs as they want, dipping the pineapple skewers into the hot chocolate sauce.