Combine flour, baking soda, salt, baking powder, cinnamon, and ginger in a large bowl; sift, and set aside.
In the bowl of an electric mixer fitted with the paddle attachment, combine butter and sugar. Beat, starting on low speed and increasing to high, until mixture is fluffy, about 2 minutes; scrape the sides of the bowl down once with a rubber spatula. Add eggs, one at a time, and vanilla; beat on medium speed until just combined, scraping down the sides of the bowl after each addition.
Turn off mixer. Add molasses, and mix on medium speed until just combined. Scrape sides of the bowl, and add dry ingredients. Mix, starting on low speed and increasing to medium high, until ingredients are just combined, about 30 seconds.
Transfer dough to a clean work surface. Roll the dough into four 1 1/2-inch-diameter logs. Wrap in parchment or plastic wrap, and refrigerate until firm, 1 to 2 hours.
Heat oven to 350 degrees. Unwrap, and slice each log into 3/8-inch-thick rounds. Place rounds on parchment-lined baking sheets. Bake until cookies crack slightly on the surface, 12 to 15 minutes. Remove from oven, and let cool on the baking sheet for 2 minutes before transferring to a cooling rack.
When completely cool, decorate with royal icing mixed with desired food coloring.
To make royal icing thicker, add more confectioners' sugar; for thinner icing, add another egg white.