Pre-heat oven to 350 degrees. Grease a 6.25" cast iron skillet with coconut oil and set aside.
In a food processor, combine chickpeas, peanut butter, maple syrup, almond milk, vanilla extract, baking powder, cinnamon and salt. Pusle until chickpeas are completely broken down and smooth.
Remove batter from food processor and fold in oat flour and dark chocolate chips until just mixed. Pour batter into greased skillet and spread evenly. Top with a few extra chocolate chips if desired and push down slightly into the top of the batter.
Bake at 350 degrees for about 20 minutes or to desired done-ness. (A couple minutes less will yield a cookie dough like center and a few more minutes will yield a less gooey cookie.)