Preheat your oven to 350°F (175°C).
Add all the wet ingredients in a large bowl (egg, butter, sweetener, and vanilla) and beat until smooth. Add the cocoa powder and mix well.
Add the dry ingredients (oat flour, baking soda, baking powder, and salt) and stir well.
Fold in the chocolate chips.
Form the dough into balls and place on a buttered cookie sheet. Leave some space between each ball for the cookies to expand. Gently press down on each ball to flatten slightly.
Bake for about 8-10 minutes, until just set. Don't over-bake or your cookies will be hard!