Wash your apples, and using a melon baller or spoon, scoop out the core of the apples from the top, creating a hole. Be careful not to scoop all the way to the bottom. You don't want your filling to leak.
In a small bowl combine brown sugar, cinnamon, nuts and raisins. Pack the filling into the apples.
Place the filled apples into a shallow baking dish or individual ramekins. Drizzle the butter evenly over the filling in each apple.
Bake for 15 minutes or until the apples are tender, and the sugar and butter have started to caramelize.
Remove from the oven and allow to cool slightly before serving.