Preheat the oven to 180°C (350°F) and line a large baking sheet with parchment paper.
In a large bowl, whisk together the flour, cocoa, baking soda, vanilla, and salt.
In another dish, whisk the coconut oil and maple syrup, then add the egg and whisk again until fully combined.
Stir the coconut oil mixture into the flour mixture, mixing until no streaks of flour remains. Stir in the chocolate to evenly incorporate.
Scoop the dough, around 2 tablespoons per cookie, onto the baking sheet. Flatten each cookie slightly with your palm (wet your hands to prevent sticking).
Bake for 8-10 minutes or until the tops are cracked and the edges are just firmed. Don't over-bake.
Cool the cookies for ten minutes on the pan before removing and cooling completely on a rack. They'll keep in an airtight container for at least three days and freeze well.