Preheat oven to 350 degrees. Line two baking sheets with parchment paper. Place the confectioners' sugar in a brown paper bag.
In a medium bowl, combine flour, pepper, cinnamon, allspice, nutmeg, cloves, and baking soda. Set aside.
Place butter, brown sugar, and molasses in the bowl of an electric mixer fitted with paddle attachment. Beat on medium speed until fluffy, about 3 minutes. Beat in egg and vanilla. With mixer on low speed, add flour mixture; beat until just combined. Pinch off dough in tablespoon amounts; roll into 1 1/4-inch balls. Arrange balls 1 1/2 inches apart on prepared baking sheets. (Dough can be frozen at this point, covered tightly with plastic wrap, up to 1 month.)
Bake until cookies are golden and firm to the touch with slight cracking, about 15 minutes, rotating sheets halfway through. Transfer sheets to a wire rack to cool slightly, about 10 minutes. Working in batches, place cookies in paper bag; shake until well coated. Let cool completely on wire rack. Store in an airtight container.