In a medium bowl, sift together flour, ground ginger, cinnamon, cloves, nutmeg, and cocoa.

In bowl of mix master, beat butter and grated ginger until whitened, about 4 minutes.

Add brown sugar; beat until combined. Add molasses; beat until combined.

In a small bowl, dissolve baking soda in boiling water. Beat half of flour mixture into butter mixture. Beat in baking-soda mixture, then remaining half of flour mixture. Mix in chocolate; turn out onto a piece of plastic wrap. Pat dough out about 1 inch thick; seal with wrap; refrigerate until firm, 2 hours or more.

Heat oven to 325 degrees. Roll dough into 1 ½ inch balls; place, two inches apart, on baking sheet. Bake until the surface cracks slightly, 13 to 15 minutes; let cool 5 minutes; transfer to a wire rack to cool completely.