Make the filling: In a large skillet, heat oil over medium heat. Add annatto seeds and heat for 1 minute to release their orange color. Remove from heat and drain the oil into a separate container. Discard the seeds and return half of the oil to the skillet.
Return the skillet to medium-high heat and add pork and fatback (or bacon). Cook, stirring occasionally, until browned, about 5 minutes. Add tomatoes, onion, bell pepper, aji dulces (if using), garlic, culantro, and oregano, and cook for 5 minutes.
Stir in chickpeas and olives (with their respective liquids) and capers (if using). Cover and simmer over low-medium heat for 40 minutes. When done, uncover and allow to cool. Drain the broth into a separate container and set aside.
Make the dough: Peel plantains and bananas, first cutting off the ends and running a knife tip lengthwise along one or more of the ridges. Insert and run a thumb just beneath the cut peel to lift and remove it. Peel the yautia. Place plantains, bananas, and yautia in a large bowl with salted cold water to prevent discoloring. You can grate them using the fine side of a hand grater or cut into 1/2- to 1-inch pieces for the processor. Fill one-third to one-half of a food processor or blender container with the cut vegetables, slowly adding some of the reserved broth to form a smooth, porridge like mash. It should not be runny. Transfer the puree to a large bowl. If you run out of broth, substitute water as needed. Stir in the salt and the remaining annatto oil.
Assemble the pasteles: Cut off 20 sheets of parchment paper 12 x 18 inches. Place a banana leaf on a sheet of parchment. Drop a scant 1/2 cup of the dough onto the center of the leaf and spread it several inches all around with the back of a spoon.
Drop 2 tablespoons of the filling a bit off center. Fold each long side and then the ends toward the center. Slide the encased leaf toward the long edge of the parchment and wrap again. Fold end flaps over. With kitchen string, tie two pasteles together, with folded edges facing each other.
Bring a large kettle of salted water to a boil. Cook the pasteles in batches of 4 to 6 tied bundles, semi covered, over medium-high heat for 30 minutes. Turn the bundles over and cook 40 minutes longer. Drain them well, remove the strings and wrappings, and serve hot.