Preheat the oven to 180° C.
Core the apples so that you can fit the raisins, walnuts and Brie inside them.
Stuff the apples with the raisins and some of the chopped walnuts to begin with, making sure you have enough chopped walnuts to sprinkle over the top of them later.
Bake for 20-25 minutes until the apples are soft and the cheese has melted up out of the core.
Preheat the grill to hot.
Sprinkle the remaining walnuts on top and grill the apples for 1 minute before transferring to a serving plate and garnishing with the whole walnuts.