Preheat the oven to 350ºF and line a 9-inch square baking dish with parchment paper. In a large food processor fitted with an S-blade, process the rolled oats briefly, until they resemble a coarse flour.
Add in the black beans, almond butter, cacao powder, ground flax, vanilla, sugar, vinegar (which helps the brownies rise), salt, and baking soda. Process until a very smooth and thick batter is formed, stopping to scrape down the sides at least once to make sure everything is mixed evenly.
Use a spatula to transfer the batter into the lined 9-inch baking dish. The batter will be rather thick, so you'll need to use the spatula to spread it evenly into the pan. Sprinkle the chocolate chips over the top, and press them lightly into the batter.
Bake until the top begins to crack and the center feels relatively firm to a light touch, about 30 minutes. Allow the brownies to cool completely before attempting to cut them into squares, as they are fragile when warm.
Serve at room temperature, and store any leftovers in an airtight container in the fridge for up to a week. (I imagine these would freeze well, too!)
You can leave out the rolled oats for a grain-free dessert. They are just slightly more gooey and fragile that way.