Place butter and sugar in the bowl of a stand mixer and mix on low speed until light, airy, and creamy, 3 minutes. Meanwhile, combine flour, cinnamon, ginger, salt, and baking soda in another mixing bowl, and set aside. Turn the mixer off, scrape down the sides, add the egg and molasses, and continue mixing until incorporated. Add the dry ingredients, a little at a time, until just combined. Chill for 30 minutes. Preheat oven to 325 degrees F.
Dip an ice-cream scoop in water (to prevent sticking), scoop dough, then roll in cinnamon sugar. Place cookies on a baking sheet lined with parchment paper, giving each one plenty of room (so they cook evenly), and bake 20–25 minutes.
Cookies are done when crispy on the outside and soft in the center. Remove from oven, cool on a wire rack, and serve.