Pre-heat oven to 375 degrees F
Start by coring the apples: while holding onto the apple, carefully push the apple corer into the apple without going through the apple. Carefully remove the core and discard it. Now, using the back of a spoon, begin to scoop out the insides of the apple so it is more hollow. This does not have to be perfect, and you want to make sure not to break through the apple. Do this for each apple (they will begin to brown, do not worry).
In a bowl, mix together the brown sugar, cinnamon and pepitas (or whatever chopped nuts you choose to use).
Cut the brie cheese into pieces big and long enough to fit inside of the apple holes (kind of like long spears, see images above). Fill the rest of the hole with the brown sugar/cinnamon mixture until it is filled to the top of the apple.
Place the apples inside of a baking dish and fill the baking dish with 1/2 cup boiling water. Place the dish immediately in the oven and bake for about 40 minutes, depending on the size of your apples.
Once you remove the baking dish from the oven, you will notice that there is a gap between the top of the filling and the hole of the apple. Fill this with extra brown sugar mixture and allow it to melt.
If you are not making eyeballs, you can enjoy your baked stuffed apples now. If you ARE making eyeballs, allow the apples to cool for around 30 minutes before drawing on your frosting eyeballs. I made a white circle over the apple hole, placed a black dot in the middle for the pupil, then added red veins.
Serve and enjoy!