Mix the condensed milk with the cocoa powder and place the mixture over medium heat.
Add the butter and chocolate, stirring until the mixture begins to loosen from the bottom of the pot.
Add the heavy cream and continue stirring until the mixture again begins to loosen from the bottom of the pot.
After cooling, make small balls, roll them in the sprinkles and place them into small cupcake wrappers.
Use the halved wafers to make the bat wings, the white sprinkles to make the eyes and the melted chocolate to fill in the irises of the eyes.