Preheat oven to 350 and line a baking sheet with parchment paper.
In a medium bowl, whisk together the flour, baking soda, salt, cinnamon, ginger, allspice, cloves and pepper. Set aside.
In a large bowl with an electric mixer or the bowl of a stand mixer with a beating blade, beat together the butter and brown sugar until creamy. Add eggs one at a time, mixing well after each addition and scraping down the sides of the bowl as needed. Add the vanilla and beat in. Add the molasses and mix in. Add the flour mixture and mix until flour is all incorporated.
Spoon batter on to prepared baking sheet, making two logs about 2 inches wide by 12 inches long and flattened on the top. Allow as much space in between the two logs as you can, as the batter will spread. *Tip: rinse your hands under running water. Shake but do not dry. Use your damp fingers to smooth the logs before baking. Sprinkle logs generously with icing sugar.
Bake in preheated oven for 30 minutes. Remove from oven, but leave oven on. Allow to cool on the baking sheet for 5 minutes, then remove to a cutting board. Cut into 1/2-3/4 inch thick slices. Return the slices to the baking sheet, standing them upright and bake a further 10 minutes. Remove from oven and then transfer biscotti to a cooling rack to cool completely before storing in a container. For really hard biscotti, you can bake a few minutes longer and/or allow biscotti to sit at room temperature to dry out for several hours before storing.
Be sure to read the "Cook's Notes" in the original post, for more tips, options, substitutions and variations for this recipe!