In a medium bowl, whisk together the flour and salt.
In a large bowl, use a stand mixer to beat the butter and sugar until creamy and smooth.
Mix in the vanilla extract and egg until fully combined.
Gradually add the dry ingredients to the wet mixture, beating until the dough comes together.
Once the dough becomes stiff, finish kneading it gently by hand.
Shape the dough into a ball, then flatten it into a ¾-inch thick disk.
Wrap the dough tightly in plastic wrap and chill in the fridge for 2 hours.
Preheat the oven to 350°F.
On a lightly floured surface, roll out the dough to ¼ inch thick and cut into shapes using cookie cutters.
Place the cutouts on a baking sheet lined with parchment paper or a silicone mat.
Chill the shaped cookies in the fridge for 5–10 minutes before baking to help them hold their shape.
Bake for 8–10 minutes, cool on the baking sheet briefly, then transfer to a wire rack to finish cooling.
Royal Icing
In a large bowl, combine the confectioners’ sugar and meringue powder.
Add warm water, one spoonful at a time, mixing on low speed.
Stir in the vanilla extract and keep mixing until the icing looks glossy.
Continue beating on low speed for 5–7 minutes, then tint with desired colors.
Spoon into piping bags.
Decorate your cooled cookies.
Notes
If the dough has been chilled for more than 2 hours, let it sit on the counter for about 15 minutes before rolling it out.
Each icing color needs two consistencies: one thicker for outlines and edges, and one thinner for flooding. Add a little more water to thin the icing as needed.
For thicker icing, snip just a small opening in the piping bag—about 1/16 inch. For thinner icing, make it slightly larger, around ⅛ inch. You can always cut more if needed.
After decorating, use a craft heat gun about 10 inches away to help set the icing and prevent it from caving in.
I like to let my cookies air dry in a cool place for about two days before packaging.
You can freeze the dough or cookies (decorated or undecorated) at any stage. For decorated cookies, freeze them slowly—place on a baking sheet for 30 minutes, then stack similar shapes with parchment between layers. Wrap in Press’n Seal, then aluminum foil, label with the date, and they’ll stay fresh for up to 4 months.