Preheat oven to 375°F (190°C). Line baking sheets with parchment paper or silicone liner.
Using an electric mixer on medium speed, beat the butter and confectioners' sugar until light and fluffy.
Mix in the egg and vanilla.
Reduce mixer speed to low. Gradually add the flour, mixing just until combined.
Transfer the dough to a pastry bag fitted with a large star tip.* Pipe the dough into circles about 2 inches in diameter. Leave about 2 inches between cookies.
Sprinkle each cookie with granulated sugar or sanding sugar.
Refrigerate the pans of cookies for 15 minutes.
Bake, one pan at a time, 14 to 18 minutes, or until the edges are just browned.
Cool on the pan on a wire rack for 5 minutes. Then transfer the cookies to a wire rack to cool completely.
Video
Notes
*The cookies pictured were made with a Wilton 1M tip. Most any tip at least that large should work. If you don't have a pastry bag, you can use a zip-top bag with the corner snipped instead.
Recipe slightly adapted from McCormick.
Store in an airtight container at room temperature up to a week.