Preheat oven to 350°. Put black beans, olive oil, spinach, applesauce, eggs, egg yolk, sugar, cocoa, and espresso powder in a food processor; pulse for 1 minute or until smooth. Microwave bittersweet chocolate and butter in a glass bowl, stirring every 30 seconds or until smooth; cool for 5 minutes. Add chocolate, vanilla extract, and salt to processor; pulse to blend. Transfer to a bowl. Stir in flour and mini chocolate chips. Pour into an oiled 9- x 13-inch pan; top with chopped pecans. Bake for 25-30 minutes; cool for 15 minutes.