Preheat the oven to 350 F. Prepare two cookie sheets with parchment paper.
In the bowl of a stand mixer fitted with the paddle attachment, or using a hand mixer, beat the butter, salt, vanilla and spices if using. Add the brown sugar and beat until creamy, a full minute.
Add the egg yolks and beat until light and airy, another minute. Pour in the molasses and beat to combine.
Sift in the cocoa, flour and baking soda. Beat until the dough is just combined. At this point you can bake the cookies right away or, if you've used overly melty butter or european style butter, set the dough aside for 30 minutes at room temp.
Portion scoops of dough onto prepared cooking sheet in 2 tablespoons of dough per cookie, leaving room for the cookies to spread (about an inch around each dough ball). Roll the balls between your hands to smooth the dough over then dip the tops of them in bowl with the extra granulated sugar for rolling.
Bake until the cookies spread, have set edges and puff up and crack in the oven, about 10-12 minutes.