In a small saucepan, bring prunes and 2 cups of water to a boil over high heat. Reduce heat and simmer, uncovered, until prunes are very soft, about 20 minutes. Drain.
Meanwhile, preheat oven to 350 degrees F. Place 16 paper liners in two muffin pans. Alternatively, lightly butter a 5x9-inch loaf pan and line bottom with a piece of parchment paper, cut to fit.
In a food processor, whirl prunes and bananas until very smooth. Add eggs and whirl to combine.
In a large bowl, sift together flour, cocoa, baking powder, cinnamon, and baking soda. Stir in banana mixture until evenly moistened. Stir in chocolate chips and banana chips, if making a loaf. Scrape the thick batter into pan and spread level.
Bake muffins for 15-20 minutes or until a toothpick inserted in the center comes out a little chocolately but not gooey. For the loaf, this may take 40 to 50 minutes. Loosen bread from pan with knife and invert onto a rack. Remove parchment. Turn bread right-side-up and let cool at least 1 hour before slicing.