Preheat the oven to 350°F. Line two cookie baking trays with unbleached parchment paper.
In a large mixing bowl, cream together the butter and egg. Next add the vanilla extract, coconut sugar, salt, baking soda, and baking powder. Beat until smooth.
Add the cassava flour. Beat until the batter is smooth. Add the oat flour and stir until everything is combined. The batter will be too thick to easily beat at this point. Fold in the chocolate chips.
Divide the dough into 12 pieces. Place six dough pieces on each cookie tray. Use a spoon to shape the dough into domed cookies.
Bake for 10-12 minutes. The cookies should be light brown around the edges. Cool for 10 minutes before transferring to a cooling rack. Cool completely before storing in an airtight container.
Optional: As soon as the cookies come out of the oven, press additional chocolate chips onto the tops of the cookies.