Preheat oven to 350°F (175°C). Line baking sheets with parchment paper.
In a large bowl, cream together the butter and sugar until light and fluffy.
Beat in the eggs one at a time, then stir in the vanilla.
In a separate bowl, whisk together the flour, baking powder, and salt. Gradually add the dry ingredients to the wet ingredients, mixing until just combined.
Roll out the dough on a lightly floured surface to about 1/4 inch thickness. Cut out cookies with Halloween-themed cookie cutters.
Place cookies on the prepared baking sheets and bake for 8-10 minutes, or until the edges are lightly golden.
Let cool on baking sheets for a few minutes before transferring to a wire rack to cool completely.
While cookies are cooling, prepare the frosting. In a large bowl, beat together the powdered sugar, butter, milk, and vanilla extract until smooth and creamy. Divide the frosting into separate bowls and tint each bowl with different food colorings.
Once the cookies are completely cool, decorate with the frosting and sprinkles.
Notes
Store cookies in an airtight container at room temperature.