Sugar Cookies

In the bowl of an electric mixer fitted with the flat beater, beat together the butter and sugar on medium speed until light and fluffy, about 4 minutes. Add the egg yolks one at a time, beating well after each addition. Cut the vanilla bean in half lengthwise and, using a small, sharp knife, scrape the seeds into the butter mixture. If using vanilla extract, add it now. Mix well.

In a sifter, combine the flour, baking powder and salt. Sift the flour mixture directly onto the butter mixture. Reduce the speed to low and beat until well mixed.

Turn the dough out onto a work surface and divide into 4 equal portions. Shape each portion into a ball, then flatten the balls into disks. Wrap in plastic wrap and refrigerate overnight. (The dough can be prepared up to 3 days ahead.) Let it soften slightly at room temperature before continuing.

Position a rack in the upper third of an oven and preheat to 350°F. Butter 2 large baking sheets.

On a lightly floured work surface, roll out a dough disk 1/4 inch thick. Using cookie cutters, cut out desired shapes. Transfer the cutouts to the prepared baking sheets. Gather up and reroll the scraps and cut out more cookies. Repeat with the remaining dough disks.

Bake until the cookies are golden on the edges, about 8 minutes. Transfer the cookies to wire racks and let cool completely. Decorate the cookies as desired with colored sugars and decorating pens. Store in an airtight container at room temperature for up to 1 week.