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 black beans until smooth.
To the pureed black beans, add in the almond butter, cacao powder, ground flax, vanilla, sugar, vinegar, 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.
Add the chocolate chips to the batter and pulse a few times to mix them in. Use a spatula to scoop 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.
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 very fragile when warm.
Serve at room temperature, and store any leftovers in an airtight container in the fridge for up to a week.