Sanding sugar is coarser than granulated sugar and adds sparkle to finished baked goods.
Heat oven to 350 degrees. Line two baking sheets with parchment paper, and set aside. In a medium bowl, whisk together flour, baking soda, salt, ginger, allspice, and white pepper; set aside.
In the bowl of an electric mixer, combine butter with light-brown and granulated sugars until light and fluffy. Beat in molasses and egg; mix well. Add the reserved dry ingredients, and beat until just combined. Form dough into a ball, and cover with plastic wrap; refrigerate until firm, at least 2 hours or overnight.
Remove dough from refrigerator. Using an ice-cream scoop, shape dough into 2-inch-diameter balls. Pour sanding sugar into a large bowl, and roll balls in sanding sugar, coating well. Place cookies on prepared baking sheets, spaced 4 inches apart; flatten each into a 3-inch-diameter disk.
Transfer to oven, and bake until brown, 12 to 15 minutes. Remove from oven, and transfer to a wire rack to cool. Store in an airtight container up to 2 days.