Preheat oven to 350 degrees F. Grease 9x13 cookie sheet and set aside.
With the paddle attachment to your stand mixer, mix brownie mix, oil, eggs, and water until well combined.
Bake for 30-35 min until a toothpick inserted in the center of a brownies comes out clean.
Let brownies cool completely, cut into 12 squares and transfer to a baking tray.
Melt white chocolate in a small bowl by heating 30 seconds at a time and stirring in between.
Spoon a small amount of melted chocolate on the top of each brownie square.
Use black food coloring and a toothpick to make ghost faces on 12 jumbo marshmallows.
Place each marshmallow in the middle of the brownie to create the melted ghost look.