Preheat oven to 180°C (350°F) and fold a 15 cm x 15 cm (7 inch x 7 inch) brownie pan with parchment paper.
Drain and rinse canned chickpeas, or skip if you are using cooked chickpeas.
Add all ingredients to a bender - chickpeas, oats, cocoa powder, nut butter, maple syrup, milk, vanilla extract, baking powder and a pinch of salt. Process until smooth, mixing in little more milk in case the batter is too thick.
Transfer the brownie batter to the prepared baking pan and top with chocolate chips if you desire.
Bake in hot oven for 18 to 25 minutes, or until the brownies are firm inside but still fudgy. Do not overbake. Remove from the oven and let cool at room temperature before serving.