Preheat a barbecue for medium heat, then lightly oil the grate.
Heat 6 tablespoons butter, sugar and nutmeg in a pan over medium heat, stirring until sugar is dissolved, about 5 minutes. Brush pineapple spears with butter mixture.
Arrange pineapple on preheated barbecue and cover; cook until lightly browned, turning occasionally, 7 to 10 minutes. Transfer pineapple to a platter.
To make the butterscotch sauce: Melt 115g butter in another saucepan over medium heat. Stir in brown sugar and cream. Bring to the boil, stirring constantly. Remove from heat and add vanilla extract and salt. Serve pineapple topped with cream sauce and ice cream.