In a large bowl, stir together the oat flour, baking powder, salt, and cocoa powder until well combined. Stir the flour mixture, along with the chocolate chips into the peanut butter mixture until well combined. The dough will be quite sticky.
Roll the dough into a ball and place onto the prepared cookie sheet. Pat into a circle that is about 9 inches in diameter.
Bake until the edges just feel set, about 15 minutes. Let cool on the pan.
Once cookie has cooled, mix together the frosting ingredients in a small bowl and spread on top of the cookie. Sprinkle with additional mini chocolate chips and DEVOUR.