Heat the oven to 350°F (175°C). Line an 8-inch square baking pan with parchment paper, leaving a little overhang for lifting, or grease the pan thoroughly.

Drain the black beans, rinse them very thoroughly under cool running water, and pat them dry with a clean towel. Removing excess liquid helps prevent a gummy batter.

Add the beans, oats, cocoa powder, maple syrup, melted oil, vanilla, baking powder, and salt to a food processor or high-powered blender. Process until completely smooth, scraping down the sides as needed.

Fold the chocolate chips into the smooth batter by hand, or pulse them briefly if you prefer a more blended chocolate flavor. Do not process longer than necessary once the chips are added.

Spread the thick batter evenly in the prepared pan and smooth the top. Sprinkle extra chocolate chips over the surface if desired.

Bake for approximately 20 to 25 minutes, until the edges look set and the center remains slightly soft. Fudgier versions may be ready closer to 18 to 20 minutes.

Let the brownies cool completely before cutting. For the firmest, fudgiest texture, refrigerate them for 1 to 2 hours after they have cooled.