Whisk the flour, cocoa powder, and baking powder in a medium bowl until evenly mixed.

In a separate bowl, stir together the granulated sugar, egg, oil, and vanilla extract until smooth.

Combine the wet and dry mixtures and stir until a thick dough forms. Cover and chill for 30 minutes.

Heat the oven to 350°F and line a baking sheet with parchment paper. Place the powdered sugar in a small bowl.

Scoop rounded teaspoons of dough, roll each into a ball, then roll in the powdered sugar to coat fully. Place on the baking sheet and gently flatten each ball into a slight oval shape.

Bake for 10 to 12 minutes until the tops show fine cracks. Let the cookies cool on the sheet for 5 minutes before moving to a wire rack.

Melt the chocolate chips in a small microwave-safe bowl in 20-second bursts, stirring between each until smooth. Spoon the melted chocolate into a zip-top bag, snip a tiny corner, and pipe simple bat wing outlines on each cooled cookie.