Preheat the oven to 350°F (175 °C). Prepare a couple of baking sheets by lining them with parchment paper. Set aside for later.
In a medium bowl, mix together the flour, cocoa, baking soda, salt, cinnamon, ginger, black pepper, and cloves. Set the whisked dry ingredients aside for later.
In the bowl of an electric mixer fitted with the paddle attachment, cream the butter and the granulated sugar for a couple minutes. Scrape down the bowl as needed.
Add the vanilla and the treacle or molasses. Beat the mixture until it is smooth.
Add the egg, and beat to incorporate it, scraping down the bowl as needed.
With the mixer on low, add the flour mixture slowly. Continue mixing until the cookie dough has come together and you can no longer see any flour. Be sure to scrape up the bottom of the bowl because some flour could be hiding, unmixed, down there.
Put the remaining 50 grams of sugar in a shallow bowl.
Roll scoops of spiced chocolate cookie dough into balls and then coat them in sugar. Place each sugar-coated scoop of dough on a cookie sheet, spacing them out every 1.5 inches. You should be able to fit 8 per half-sheet pan.
Bake the cookies for 10–12 minutes. Let cool for 5 minutes to firm up before transferring to a rack to cool completely.
Let cool completely before serving.
Notes
Use Dutch-processed cocoa powder, which has a darker colour and richer flavour. Natural cocoa powder is more acidic and may affect the texture and appearance of these cookies.
If your chocolate cookie dough is too soft, you may chill it briefly for about 30 minutes. I have never needed to, but you may have to especially if your kitchen is warm.
Use a ¾ ounce scoop to evenly portion out perfect scoops of dough. You can smooth them out by rolling them briefly between your palms.
Do not overbake these cookies because they will dry out.
These cookies are best eaten within 2–3 days because they may dry out and become more crispy.