In a large bowl, mix together the dry ingredients - flour, cocoa powder, baking powder, baking soda, salt, and cinnamon - and set aside.Blend the dates or prunes using a blender or food processor. Add the bananas, eggs, and vanilla and blend just until incorporated. Be sure to scrape the sides to get all the prune/date puree also.Mix the wet ingredients with the dry ingredients and stir well, then add in the chocolate chips.Divide into muffin cups (I use silicone muffin liners), and bake on 325 for about 18 minutes. Test with a toothpick and remove from oven if toothpick comes out clean.