Preheat the oven to 350°F. Generously coat your ghost pan with baking spray (I like Baker’s Joy).
Mix up the brownie batter according to the package directions and spread it evenly into the pan. Scatter with Halloween sprinkles.
For shallow pans that bake quickly, place the ghost cookies right on top before baking. For deeper pans, wait until the brownies are about halfway done, then gently press the cookies in so they don’t overbake.
Once baked, let the brookie cake cool completely in the pan.
For parties or a group, flip the entire pan onto a platter so the ghost shape really shows off. Set it out whole and let your guests slice it into spooky squares.