These soft and buttery shortbread cookies make the perfect halloween ghost cookies. They hold their shape when baked making them easy to cut out and create frosted shortbread cookies for any occasion.
Line cookie sheets with parchment paper or nonstick baking mat. Set aside.
Beat butter just until creamy, slowly add powdered sugar and beat until combined. Add about half the flour and beat, continue adding flour a bit at a time until you have a stiff dough. Sprinkle a bit of the remaining flour on work surface, transfer dough onto the flour and sprinkle remaining flour onto the dough. Knead dough until all the flour is incorporated (edges may begin to crack and that is fine). Roll dough to desired thickness, about an 1/8 of an inch, and cut out shapes using cookie cutter. Gather up scraps, re-roll and cut more shapes until all the dough is used up.
Place cut outs onto prepared baking sheet, cover with plastic wrap and chill in the refrigerator for 30 to 40 minutes. During the last 10 minutes preheat oven to 275℉
Remove from the refrigerator, take off plastic wrap and bake for 20 to 30 minutes, just until edges are slightly beginning to turn golden. Remove from oven cool on cookie sheet for 5 minutes and then transfer to cooling rack to cool completely before frosting.
To Make Frosting
Beat sugar on medium speed of electric mixer until light and fluffy. About 3 to 4 minutes. Turn mixer to low and slowly add 1 cup of the powdered sugar, beating until well combined. Add milk, and beat to combine. Scrap down sides and bottom of the bowl as necessary. Add remaining powdered sugar, beating well. Add additional powdered sugar or milk as required to achieve a fluffy frosting that will pipe easy but still hold its shape.
Fit piping bag with a Wilton #18 star tip and fill with frosting. Starting at the top of the cookie, with a steady hand, pipe rows of frosting back and forth as you work your way down the cookie, continuing the pressure on the bag as you go.Set cookies aside to air dry the frosting or chill in the refrigerator. Store in single layers between parchment paper in an airtight container for up to 3 days or freeze for up to 2 months.