Preheat the oven to 350 degrees F (175 degrees C). Grease a 9-inch round cake pan.

Place chocolate chips in a microwave-safe bowl. Microwave until chocolate melted and smooth, about 2 minutes, stirring every 20 seconds after 1 minute. If you have a powerful microwave, reduce the power to 50 percent.

Combine garbanzo beans and eggs in the bowl of a food processor; process until smooth. Add sugar and baking powder; pulse to blend. Pour in melted chocolate; process until smooth, scraping corners to make sure chocolate is completely mixed. Transfer batter to the prepared cake pan.

Bake in the preheated oven until a knife inserted into the center comes out clean, about 40 minutes. Cool in the pan on a wire rack for 10 to 15 minutes before inverting onto a serving plate. Dust with confectioners' sugar just before serving.