In a medium bowl, whisk together the dry ingredients.
In the bowl of a stand mixer (or using a hand mixer), add the shortening and sugar. Mix on medium speed for 2 minutes until thoroughly creamed. Add the egg, vinegar and molasses and mix to combine. Scrape down the sides of the bowl then, with the mixer running on low, slowly add the dry ingredients. Mix until totally combined.
Scrape the dough onto a work surface and divide it in half. Working with one portion at a time, roll or press the dough ¼-inch thick between 2 large sheets of parchment paper. Leaving the dough sandwiched between the parchment paper or plastic wrap, stack the dough on a baking sheet and refrigerate for 4 hours or overnight. (You can also freeze the dough for 15-20 minutes.)
Preheat the oven to 375F. Line two baking sheets with parchment paper or silicone liners.
Remove one dough sheet from the freezer or refrigerator and place on the counter. Working quickly, peel off the top parchment paper then cut into the desired shapes. Use a thin metal spatula to help transfer the cookies to the baking sheets.
If the dough begins to stick you can put it back in the freezer for a bit before continuing. Repeat with the remaining dough. The scraps can be rolled out to get as many cookies as you can.
Bake for 9-10 minutes until set. Let cool for 3 minutes on the baking sheet then transfer to a wire rack to cool completely. Decorate with royal icing or frosting if desired - enjoy!