01 - Preheat oven to 350°F. Line a 12-cup muffin tin with cupcake liners.
02 - Cream butter and sugar until light and fluffy. Beat in eggs one at a time, then vanilla. Whisk flour, baking powder, and salt in a separate bowl. Add half the dry mixture to the wet, followed by milk, then remaining dry ingredients until just combined.
03 - Divide batter evenly among liners, filling each 2/3 full. Bake for 18-20 minutes or until a toothpick inserted comes out clean. Cool completely on a wire rack.
04 - Beat butter until creamy. Add powdered sugar and cocoa powder, mixing slowly. Add vanilla and milk, beating until smooth and spreadable.
05 - Arrange cooled cupcakes close together on a serving tray in a rectangle. Generously spread chocolate frosting over all cupcakes to create a smooth surface.
06 - Crush chocolate sandwich cookies and sprinkle over frosting for dirt. Write RIP and spooky messages on rectangular cookies with gel icing pens. Press tombstones into cupcakes. Decorate with gummy worms, candy pumpkins, or Halloween candy.
07 - Chill briefly before serving to set decorations.