1. In a small saucepan, bring prunes and 2 cups water to a boil over high heat. Reduce heat and simmer, uncovered, until prunes are very soft, about 20 minutes. Drain.
2. Meanwhile, preheat oven to 350°. Lightly butter a 5- by 9-in. loaf pan and line bottom with a piece of parchment paper cut to fit.
3. In a food processor, whirl prunes and bananas until very smooth. Add eggs and whirl to combine.
4. In a large bowl, sift together flour, cocoa, baking powder, cinnamon, and baking soda. Stir in banana mixture until evenly moistened. Stir in nuts, banana chips, and chocolate chips. Scrape the thick batter into pan and spread level.
5. Bake bread until a toothpick inserted in the center comes out a little chocolaty but not gooey, 45 to 50 minutes. Loosen bread from pan with a knife and invert onto a rack. Remove parchment. Turn bread right side up and let cool at least 1 hour before slicing.
Shortcut: Substitute 12 oz. (1 1/2 cups) unsweetened prune baby food for the pitted prunes, and omit water and cooking in step 1.
Note: Nutritional analysis is per slice.