Heat the oven to 350°F and line a baking sheet with parchment paper.

In a mixing bowl, beat the softened butter and granulated sugar until smooth and creamy.

Add the egg yolk and vanilla extract, then mix until fully combined.

Stir in the flour, baking powder, and salt until a soft dough forms.

Roll the dough to ¼-inch thickness on a lightly floured surface and cut out ghost shapes.

Place the shapes on the prepared baking sheet and bake for 8 to 10 minutes until the edges turn lightly golden.

While the cookies cool, whisk the powdered sugar and milk until smooth, then divide the icing and tint a small portion with black food coloring.

Pipe white icing over each cooled cookie, then use the black icing to add simple eyes and a mouth.