Preheat the oven to 350℉. Line baking sheets with parchment paper or reusable silicone baking mat. Set aside.
Sift together flour, cocoa powder, and baking soda into a bowl. Whisk in salt. Set aside.
In the bowl of a stand mixer fitted with a paddle attachment (or using an electric hand mixer) cream together softened butter, brown sugar, and molasses until smooth, about 3 minutes. Scrape down the sides of the bowl as needed to ensure thorough mixing.
Add egg and vanilla. Mix on medium speed until fully incorporated.
Add flour mixture to mixing bowl. Mix on low speed until dough comes together. Scape down the sides of the bowl as needed. Be careful not to over-mix or overwork the dough.
Use a #40 scoop (1 ½ Tablespoon scoop) to portion out cookie dough.
Roll cooke dough balls into granulated sugar. Place balls 2-inches apart on prepared baking sheet. Bake for 12-14 minutes, rotating the baking sheet midway through baking.
Remove from the oven. (*Reshape cookies if needed.) Leave cookies in the baking sheet pan for 5 minutes. Then, unmold and transfer cookies to a wire rack to cool to room temperature.