Preheat the oven to 350 F and grease a 12 count muffin pan. (I used coconut oil)
Prepare the flax egg by combining 2 tbsp ground flax with 6 tbsp water. Allow this to rest and thicken for at least 10 minutes. (You can do this in the food processor itself to save time)
Once black beans are thoroughly drained, add them to the food processor.
Add the cocoa powder, baking powder, vanilla extract, sea salt, coconut sugar and maple syrup. Warm the coconut oil for a few seconds before adding to the food processor.
Pulse to combine. You may need to stop to stir and make sure everything is combined.
Add 1 tbsp water or unsweetened vanilla almond milk to ensure the batter is smooth. It should be slightly firmer than the consistency of cake batter, but not too firm.
Evenly distribute the batter into the muffin pan. Add just a few pieces of optional toppings on top of each cup. I added walnuts and dark chocolate chips. I pushed some of them in so that I could enjoy a piece in each cup.
Bake for 24-28 minutes. I checked the muffins at around 25 minutes and poked with a fork. If the fork comes out fully wet, leave it in for another few minutes. Remove the muffins just shy of fully dry.