Well-wrapped dough can be refrigerated up to three days. Soften slightly at room temperature before rolling out.
In a large bowl, beat butter and sugar on high speed until light and fluffy, about 5 minutes. Add egg; mix well. Beat in molasses, cinnamon, ginger, allspice, baking soda, and salt. On low speed, add flour a cup at a time, mixing until incorporated.
Divide dough into quarters; shape into disks, and wrap into plastic. Refrigerate until firm, about 3 hours.
Preheat oven to 375 degrees with racks in top and bottom third. On a lightly floured work surface, roll out a dough disk to 1/8 inch thick. Cut out cookies, rolling out any scraps and additional disks as needed until you have about 20 kids. Transferto parchment-paper-lined baking sheets, leaving 1 inch between cookies. With remaining dough, cut out additional kids to make clothes, jewelry, and hair as desired. Dress cookies, and refrigerate 20 minutes.
Bake cookies, two sheets at a time, 7 minutes; rotate pans top to bottom and front to back, and continue baking until cookies are firm when touched, about 6 to 8 minutes more. Let cool on baking sheets 5 minutes. Transfer to wire racks; let cool completely. Decorate cookies as desired.
