Beat the butter and brown sugar until combined and fluffy, about 2 minutes.
Add the egg and molasses and beat 2 to 3 minutes more, until light and fluffy.
Mix in the baking soda, nutmeg, ginger, and cinnamon.
Add the flour one third at a time on low speed, mixing just until incorporated.
Cover and refrigerate the dough for 2 hours.
Heat the oven to 375°F and line two baking sheets with parchment paper. Roll the chilled dough into balls and coat each in powdered sugar.
Bake for 9 to 10 minutes, until puffed and cracked but still soft in the center.
Cool on the baking sheet a few minutes, then move to a wire rack.