Preheat oven to 350 degrees. Coat a 9 x 13-inch pan with cooking spray and dust with flour OR line with aluminum foil and coat foil with cooking spray.
In a blender or mini food processor, process beans with coffee until smooth; set aside.
In a double boiler over very low heat, melt butter and chocolate.
Meanwhile, in a medium bowl, using an electric mixer, beat eggs and sugar until light and fluffy. With mixer on low speed, add melted chocolate to eggs; incorporate well. Add black bean mixture, vanilla and salt; mix well. Add flour; combine thoroughly on low speed.
Pour batter into prepared pan and bake until a tester inserted in center of brownies comes out clean, about 25 to 30 minutes. Remove pan to a cooling rack. After 10 minutes, remove brownies from pan by pulling up on foil and placing brownies on cooling rack to cool more. Cut into 24 pieces and serve.
Cook's Note: Customize this basic recipe with instant espresso, a teaspoon of cinnamon or 1/4 teaspoon of cayenne pepper. Great served with whipped cream or powdered sugar, or topped with walnuts.