Mix Dry Ingredients: In a medium bowl, mix together the flour and spices until Set aside.
Cream Butter and Sugar: In the bowl of a stand mixer fitted with the paddle attachment, beat the butter and brown sugar with the egg on medium speed until light and fluffy. This will take around 3 minutes.
Add Wet Ingredients: Mix in the molasses and vanilla until fully incorporated, scraping down the sides of the bowl as needed.
Combine with Dry Ingredients: With the mixer on low speed, gradually add the flour mixture. Mix until a dough forms.
Chill the Dough: Turn the dough onto a piece of plastic wrap, shape it into a flat disc, and wrap tightly. Chill for at least 3 hours or, ideally, overnight.
Preheat Oven: Arrange oven racks in the upper and lower thirds of the oven. Preheat to 350°F (175°C). Line two baking sheets with parchment paper.
Roll and Cut Cookies: On a lightly floured work surface, roll out the dough to 1/4-inch thickness, sprinkling flour on the surface and rolling pin as needed. Use cookie cutters to cut out shapes, then arrange them on the prepared baking sheets, leaving space between cookies. Gather and reroll scraps to use all the dough.
Bake: Bake cookies for about 10 minutes, or until firm to the touch. (Baking time may vary depending on the size of the cookies.)
Cool: Let the cookies cool slightly on the baking sheets before transferring them to a wire rack to cool completely.
Decorate (Optional): To glaze, mix powdered sugar with water to form a thin glaze. Use a pastry brush to coat each cookie and, if desired, add sprinkles. Let them dry completely before storing.