In a stand mixer or with a hand mixer, cream together the butter, shortening, and sugar on medium-high speed for 1 minute until well combined.
Add the molasses and egg, and mix on medium-high speed for another minute until well combined.
Add the dry ingredients and mix on low speed until just combined.
Chill the dough for at least 2 hours.
Scoop the chilled dough into balls and roll them in sugar. Flatten them slightly.
Bake at 375°F for 15 minutes (for cookies that are about 2.5 ounces each).