Preheat oven to 350°F and line baking sheets with parchment paper.
In a medium bowl, whisk together flour, ginger, cinnamon, baking soda, and salt. Set aside.
In a large bowl, beat butter and brown sugar until fluffy, about 2-3 minutes. Add molasses, egg, and vanilla, beating until well combined.
Gradually mix in the dry ingredients until a dough forms. Don't overmix!
Roll dough into ¾-inch balls and place 1 inch apart on prepared baking sheets.
Bake for 8-10 minutes until edges are just set. The centers will look slightly underdone—that's perfect!
Cool on baking sheet for 5 minutes, then transfer to wire racks to cool completely. Decorate with white icing if desired.