In a high-speed blender or food processor, add the black beans, maple syrup, eggs, coconut oil, cacao powder, vanilla, coffee liqueur and salt. Blend on high until completely smooth (stop and scrape the sides as needed). Add the almond flour and baking powder. Blend on low just until incorporated. Add the chopped chocolate and pulse to combine.
For the frosting, combine all of the ingredients in a bowl and gradually mix until smooth and thick. I like a not-too-sweet frosting, but feel free to add more maple syrup to taste. Spread the frosting over the brownies. Cut into 12-16 squares, and serve.
Do Ahead: The brownies can be covered and stored at room temperature for up to 3 days.