In a large bowl whisk together the first six dry ingredients and set aside.
In the bowl of a stand mixer fitted with the whisk attachment, cream the butter, dark brown sugar, and orange zest at medium speed, until light and fluffy, for at least 4 minutes.
Add the egg, molasses, and vanilla extract, scraping down the sides of the bowl. Mix until combined.
Add the dry ingredients and mix until fully incorporated.
Divide the dough into fourths. Form each quarter into a disc, and wrap with plastic. Chill the dough in the refrigerator for at least 2 hours.
Preheat the oven to 350º F and line baking sheets with parchment paper.
Remove one dough disk from the refrigerator and place it on a lightly floured surface. Sprinkle flour on top and, using a lightly floured rolling pin, roll the dough until it's 1/4-inch thick. Cut the dough using snowflake cookie cutters and transfer to a baking sheet.
Re-roll the dough and repeat the process until you have used all the disks. You can always freeze the remaining dough and prepare it during the following week.
Bake cookies for 8 to 10 minutes. Cool for a few minutes on the baking sheet before transferring to a wire rack.