Prepare the Dough: In a large mixing bowl, whisk together the flour, baking powder, and salt. In another bowl, cream together butter and sugar. Mix in egg, milk, and vanilla extract. Gradually add flour mixture until soft dough forms.

Chill the Dough: Wrap dough in plastic wrap and refrigerate for at least 30 minutes to maintain shape.

Cut and Bake Cookies: Preheat oven to 350°F (175°C). Roll out dough to ¼-inch thickness, cut ghost shapes, and freeze for 10 minutes prior to baking. Bake for 8-10 minutes until edges are golden.

Make the Icing: Combine powdered sugar, corn syrup, and milk until smooth. Adjust thickness as needed. Stir in extract.

Decorate: Outline cooled cookies with thicker icing and flood with thinner icing. Use food coloring for designs and allow to dry.