Preheat oven to 180C.
Beat the butter with the sugars until creamy (for 1 to 2 minutes). Add in the egg and vanilla, and mix until smooth.
In a separate bowl sift together the oat flour, cocoa, salt, and bi-carb soda. Add into the wet ingredients and stir (Note the dough will be a soft consistency due to the oat flour). Add in the chopped chocolate and mix together.
Roll dough into balls approx 50g in size and place on a baking tray leaving about 2 inches in between to allow for a small amount of spreading. Refrigerate for at least 30 minutes.
Bake for 10-12 minutes until edges are slightly firm.
Cool on tray for 10 minutes before transferring to a wire rack,