1. In a small bowl (not the container you're microwaving the mug cake in), mash the banana, black beans, and almond butter until smooth, about one minute.
2. Stir in the cocoa powder.
3. Pour the batter into a small mug or ramekin. Microwave for one minute. Sprinkle on the chocolate chips (if using), and microwave for another 30 to 120 seconds, until the batter is top center is almost dry. The texture will be fudgey, so don't over-microwave because it'll cause a rubbery texture.
4. Allow to cool for a couple minutes (it'll be super hot!) and enjoy as is or topped with dairy-free yogurt or ice cream.

Here's the nutritional information verywell.com [1]: