How to Make It
Heat oven to 350° F. In a large bowl, whisk together the flour, baking soda, and salt.
Using an electric mixer, beat the butter and sugar until smooth. Add the egg and beat until fluffy, about 2 minutes. Beat in the vanilla.
Reduce the mixer speed to low and gradually add the flour mixture, mixing until just incorporated (the dough will be stiff). Shape into a disk. Wrap in plastic wrap and refrigerate until firm, at least 1 hour.
On a floured surface, roll the dough to ¼ inch thick. Using cookie cutters, cut into shapes. Place on parchment-lined baking sheets, spacing them 1½ inches apart. Sprinkle with the sanding sugar, if using.
Bake until just beginning to brown at the edges, 10 to 12 minutes. Cool slightly on baking sheets, then transfer to wire racks to cool completely.
Store in an airtight container at room temperature for up to 1 week.