Preheat oven to 390 degrees F.
Halve each apple lengthwise and remove core and seeds with a small knife, spoon or melon baller.
Fill each half with the chopped chocolate.
Sprinkle with cinnamon. Place half a tablespoon of butter over each of them, and place apple halves in a baking dish. Then add the water and remaining butter into the dish.
Bake the apples for 25-30 minutes or until a paring knife cuts through the apple easily. Remove from oven.
Place 5 mini marshmallows on each apple.
Turn the broiler on and broil until golden brown. Serve the baked apples warm with vanilla ice cream or whipped cream.