In a medium bowl, whisk together flour, spices, baking soda, and salt; set aside. With an electric mixer, beat butter and brown sugar until smooth.
Beat in molasses and egg. With mixer on low, add dry ingredients; mix just until a dough forms. Place dough on floured plastic wrap; pat into an 8-inch square. Wrap well; chill until firm, 1 to 2 hours.
Preheat oven to 350 degrees. Divide dough in half. Working with one half at a time (rewrap and refrigerate other half), place dough on floured parchment or waxed paper; roll out 1/8 inch thick, turning, lifting, and flouring dough (and rolling pin) as needed. Freeze dough (on paper) until firm,
about 20 minutes.
Loosen dough from paper. Cut out shapes, and transfer to baking sheets. Decorate with sugar or sprinkles, as desired.
Bake until firm and edges just begin to darken, 10 to 18 minutes, depending on size. Cool completely
on baking sheets.
For the neatest edges, dip cutters in flour before cutting out each cookie.