Preheat oven to 350°F. Line a baking sheet with parchment paper. Set aside.
In a bowl, sift together the flour, baking soda, salt, cinnamon, ginger, allspice, cloves, and nutmeg. Set aside.
In a mixing bowl, beat together the butter and brown sugar until well combined.
Next, add the eggs and beat them into the batter until well mixed.
Pour in the molasses and the vanilla extract. Beat until combined.
Now, add the flour and beat in until just combined. The dough will be sticky.
Turn dough out onto prepared baking sheet and form into a log. (Dust your hands with flour; dough is a bit sticky!)
Form log into a rectangle shape that is roughly 5" wide and 15 " long.
Sprinkle the top of the log with the confectioner's sugar.
Bake for 30 minutes. Remove from oven and place baking sheet on a wire cooling rack so that air can circulate around the baking sheet. Allow to cool for 5 minutes.
Using the parchment paper, slide the log onto a large cutting board. Slice into 3/4" slices across the width of the log.
Place slices back onto baking sheet which has been lined with more parchment paper. Slices are cut side down. Bake for 7 minutes.
Remove from oven. Carefully turn the cookies over and bake for another 7 minutes.
Remove from oven and allow to cool on the baking sheet for 3-5 minutes. Transfer to wire cooling rack to finish cooling completely.
Package biscotti for gift-giving or pile into a food-safe container. Leave at room temperature, or freeze until needed for up to 3 months.