Step 1

For the cookies: Whisk together the flour, baking powder and salt in a small bowl. Beat the butter and granulated sugar together in a stand mixer fitted with the paddle attachment on medium speed until light and fluffy, about 5 minutes. Beat in the egg and vanilla, then turn the mixer to low and add the flour mixture. Mix until completely incorporated. Divide the dough in half, pat into 2 discs, wrap in plastic wrap and refrigerate until firm, about 1 hour.

Step 2

Position the oven racks in the top and bottom thirds of the oven and preheat to 350 degrees F. Line 2 baking sheets with parchment paper.

Step 3

Let the dough sit at room temperature for a few minutes to make rolling easier. Roll out 1 disc between 2 pieces of parchment to 1/8-inch thick. Cut out desired Halloween shapes with cookies cutters and arrange about 2 inches apart on the prepared baking sheets. Repeat with the remaining disc of dough.

Step 4

Bake, rotating and switching the positions of the baking sheets halfway through, until the cookies are just turning golden brown on the bottom, 10 to 12 minutes. Let the cookies cool on the baking sheets for 5 minutes, then transfer to a wire rack to cool completely, about 1 hour.

Step 5

Meanwhile, reroll the scraps between 2 pieces of parchment and refrigerate until chilled, about 1 hour. Repeat the cutting and baking process.

Step 6

For the royal icing: Beat the confectioners' sugar, meringue powder and 1/3 cup water in a stand mixer fitted with the whisk attachment on medium-high speed until stiff peaks form, 5 to 6 minutes. Color the icing as desired for the cookie shapes.

Step 7

To make flood icing: Remove three-quarters of the desired color icing to a small bowl and stir in 1/2 teaspoon water until flooding consistency is achieved?you can run a knife through it and it flows back to where it was in 10 seconds. Add more water, 1/4 teaspoon at a time, until you've reached the right consistency. Transfer the flood icing to a piping back fitted with a number 2 round tip. Transfer the remaining thick icing to a piping bag fitted with a number 1 round tip.

Step 8

For cats: Pipe a black border around the cat with thick black icing. Fill with black flood icing and allow to harden, 6 hours or up to overnight. Pipe 2 pointy eyes on the face with thick yellow icing. Allow to harden, about 1 hour.

Step 9

For ghosts: Pipe a white border around the ghost with thick white icing. Fill with white flood icing and allow to harden, 6 hours and up to overnight. Pipe a ghost face with thick black icing. Pipe dots around the border of the ghost with thick orange and black icing. Allow to harden, about 1 hour.

Step 10

For pumpkins: Pipe an orange border around the edge of the pumpkin with thick orange icing. Fill with orange flood icing and allow to harden, 6 hours and up to overnight. Pipe two orange lines down the pumpkin with thick orange icing. Pipe on a green stem with thick green icing. Pipe vines with thick green icing. Allow to harden, about 1 hour.

Step 11

For candy corn: Pipe a white triangle border around the top third of the cookie with thick white icing. Pipe a trapezoid in the middle portion of the cookie, bordering the white triangle, with thick orange icing. Pipe a larger trapezoid that outlines the lowest third with thick yellow icing. Fill the white triangle with white flood icing. Fill the orange trapezoid with orange flood icing. Fill the yellow trapezoid with yellow flood icing. Allow the flood icing to harden, 6 hours and up to overnight.