Spooky S’mores Bars

Preheat oven to 350°F. Butter an 8 x 8-inch pan. Line with parchment paper, letting ends overlap. Butter parchment.In a medium bowl, stir together flour, oats, graham cracker crumbs, baking powder, and salt.In a bowl of an electric mixer, beat butter and sugar together. Add in egg and mix well. Stir in flour mixture until combined.Spread into prepared pan, smooth top evenly and bake until done, about 18-20 minutes. Let cool on a wire rack.Once cooled, cover top with candy bars, breaking up fourth bar to cover cookie base completely. Top with 12 ghost-shaped marshmallows. (Place ghosts face down, as faces will melt under broiler.)Move top oven rack to the next to highest position (closer to the flame can cause parchment to burn). Set oven to Low Broil. Place bars in oven for 1-2 minutes until chocolate begins to melt and marshmallows are golden. Let cool, then use food coloring pen to add eyes and mouths to ghosts. Lift out of pan using the parchment overhang. Cut into bars. Serve warm or at room temperature.