Preheat the oven to 325°F (163°C) and line a baking sheet with parchment paper.
In a mixing bowl, whisk together the flour, cocoa powder, baking soda, salt, and sugar until evenly combined.
Add the softened vegan butter, milk, and vanilla to the dry ingredients. Cut or mash the butter into the dry mix and stir until a cohesive dough forms; it may seem dry at first but continue breaking up the butter and mixing—do not add extra milk.
Fold in the chocolate chips until evenly distributed through the dough.
Roll the dough into cookie-sized balls and place them on the prepared baking sheet, spaced a couple inches apart. For chewier cookies, cover and refrigerate the dough until cold or overnight (optional).
Bake for 14 minutes, then remove from the oven and let the cookies cool on the baking sheet until firm enough to handle.