Preheat your oven to 350°F (175°C). Grease a 9″ x 9″ baking pan with non-stick cooking spray and line it with parchment paper.
Prepare the brownie mix according to package instructions and pour into the prepared pan.
Bake according to the package directions, then remove from oven and let cool.
Heat the coconut milk (or heavy cream) in a microwave-safe bowl until bubbling, about 30-40 seconds.
Stir in the chocolate chips until melted and smooth, then let cool for about 30 minutes.
Pour the cooled ganache over the cooled brownies and spread evenly.
Melt the white candy melts in a microwave-safe bowl, then scoop dollops onto a parchment-lined cookie sheet to form ghosts and refrigerate for 15 minutes.
Decorate the ghosts with black frosting for eyes and mouths, then place them on top of the frosted brownies.
Notes
Don’t overmix the brownie batter and watch for doneness to avoid overbaking.