Grease a loaf pan and sprinkle with breadcrumbs. Preheat oven to 175 degrees.
Mix the butter with the sugar until lightly creamy. Mix in the eggs one by one. Peel the bananas and mash them with a fork, then immediately stir into the custard with the orange peel and orange juice. Grate the chocolate, mix with the flour, baking powder and nuts and stir into the batter. Pour the batter into the mold and bake for 1 hour.