In a sauce pan over medium heat, melt 4 tbsp of butter then stir in brown sugar, maple syrup and spiced rum until dissolved to form sauce. Stir in cream and then remove from heat and allow to cool.
Coat each pineapple slice on both sides using the remaining 2 tbsp of butter then grill over medium-high heat for 4-5 minutes on each side or until pineapple has golden brown grill marks on both sides.
Remove pineapple slices from grill, let cool for 1-2 minutes then top with a scoop of vanilla ice cream on each. Drizzle with cooled maple rum sauce and serve immediately.