Heat the oven to 350°F (175°C). Line an 8-inch square baking pan with parchment paper, leaving a little overhang on two sides so the cooled blondies can be lifted out easily.

Drain the chickpeas and rinse them very well under cool running water. Pat them dry with a clean kitchen towel or paper towels, since excess moisture can make the batter overly wet and gummy.

Add the chickpeas, peanut butter or almond butter, maple syrup, vanilla extract, rolled oats, baking powder, and salt to a food processor. Process until the mixture is very smooth and mostly lump-free, scraping down the bowl as needed.

Fold most of the vegan chocolate chips into the thick batter, reserving some for the top. Avoid processing the chocolate chips into the batter because keeping them whole gives the blondies pleasant melted chocolate pockets.

Transfer the batter to the prepared pan and spread it evenly into the corners. Sprinkle the reserved chocolate chips over the surface, pressing them in lightly if needed.

Bake for 20 to 25 minutes, until the edges look set and lightly browned while the center remains soft. Do not wait for the middle to look completely dry, because the blondies continue to firm as they cool.

Cool the pan completely for 30 to 60 minutes before slicing. For the neatest squares and a firmer fudgy texture, chill the blondies before cutting them into 16 small pieces.