Mix sugar, brown sugar, and molasses in a bowl. It’s fine if it’s clumpy and not perfectly mixed together. Set aside.
Whisk or sift together the flour, cocoa powder, salt, and baking soda. Set aside.
Cream the butter for 2-3 minutes until light and very creamy.
Add the sugar mixture and mix for another 2-3 minutes, scraping down the sides of the bowl as necessary.
Add the egg and vanilla extract. Mix until combined.
Add the flour mixture, and mix until just combined.Try not to over mix the dough. It should be very thick and fudgy.
Gently mix in the candy.
Once the dough is mixed, place 2 tablespoon balls of dough on a baking sheet lined with parchment. You don’t have to worry how far apart they are as we are chilling the cookie dough, not baking it. If desired, add more candy pieces to the top of the balls of cookie dough.
Loosely cover the pan with plastic wrap and chill the cookie dough in the refrigerator for at least 30 minutes. Alternatively, you can simply chill the entire bowl of cookie dough for at least 30 minutes before scooping and baking.
While dough is chilling, preheat oven to 325 ℉.
Once the dough is chilled and the oven has pre-heated, add the cookie dough balls onto a parchment or silicone mat-lined baking sheet, keeping the balls of dough 2-3 inches apart.
Bake on the middle rack of the oven, one baking sheet at a time, for 10-12 minutes, or until firm around the edges. Watch closely, since they’re so dark it can be easy to burn or over bake.
Let cool before removing from the baking sheet. They will be very soft at first, but firm up as they cool. Enjoy!