Slice apples and arrange on platter with crackers. Set aside.
Place whole wheel of brie cheese onto a baking sheet lined with parchment paper or foil. Bake 8 minutes.
While cheese is baking, place hazelnuts into a small skillet and toast over medium heat. Remove from pan onto paper towels to rub skins off.
Remove cheese from oven and place onto serving platter.
Wipe pan out and place back over medium heat. Add in water and brown sugar and stir until sugar has dissolved. Pour in toasted hazelnuts and stir to coat and sugar mixture starts to bubble. Immediately remove from heat and pour over warm brie and serve.