Cream the butter mixture. In a large bowl, beat the butter, brown sugar, molasses, and vanilla with an electric mixer on medium speed until light and fluffy.
Add the egg. Beat in the egg until fully combined.
Mix the dry ingredients. In a separate bowl, whisk together the flour, ginger, baking powder, cinnamon, nutmeg, and salt.
Combine. With the mixer on low, add the flour mixture to the butter mixture and beat just until a smooth dough forms.
Chill. Divide the dough in half, pat each half into a disc, wrap in waxed paper, and refrigerate until firm, at least 1 hour or up to overnight.
Heat the oven. Preheat to 350°F and line baking sheets with parchment paper.
Roll and cut. Lightly flour your work surface and rolling pin. Roll one disc to ¼ inch thick and cut out shapes with floured cookie cutters.
Bake. Place cookies 1 inch apart on the prepared sheets. Bake 10 to 12 minutes, until lightly browned at the edges.
Cool. Move the cookies to a wire rack to cool completely before decorating. Repeat with the second disc of dough.