Preheat the oven to 350°F (150°C) and line a large cookie sheet with parchment paper. Set aside.
Combine the finely mashed avocado, coconut palm sugar, egg (or for vegan version with flaxseed prepared as instructed in notes below), and vanilla extract in a medium-sized bowl.
In a separate bowl, whisk together the cocoa powder, flour, and baking soda.
Mix together the wet and dry ingredients until just combined, then gently stir in the dark chocolate pieces.
Using a small ice cream scoop or a spoon, add one heaping Tablespoon of dough onto the prepared baking sheet. Flatten the top a little bit and add a few more chocolate pieces on top if desired.
Bake for 8-10 minutes or until the top has set (don’t over-bake!). Remove from the oven, let cool for a few minutes on the baking tray, then transfer to a cooling rack to cool completely. Enjoy!
