Preheat the Oven: Preheat the oven to 350°F (175°C) so it is ready when the brownie mixture is prepared.
Prepare the Baking Pan: Grease a baking pan and line the bottom with parchment paper to help prevent the brownies from sticking.
Blend the Main Ingredients: Place the drained and rinsed black beans, cocoa powder, rolled oats, sea salt, plant-based milk, almond butter, vanilla, and baking powder in a food processor. Process until the ingredients are thoroughly combined and the mixture becomes relatively smooth.
Fold in the Chocolate and Nuts: Transfer the blended mixture to a suitable mixing bowl if needed. Stir in the chocolate chips or chunks and chopped macadamia nuts, distributing them evenly throughout the batter.
Fill the Baking Pan: Pour the brownie batter into the prepared pan. Spread it out evenly, then sprinkle additional chocolate chips over the surface.
Bake the Brownies: Place the pan in the preheated oven and bake for 18–20 minutes, following the source recipe's baking range. The brownies should be set enough to continue cooling in the pan.
Cool Before Cutting: Remove the pan from the oven and allow the brownies to cool completely before lifting them out and cutting them into 12 pieces. Cooling fully helps the brownies hold their shape when sliced.