Preheat the oven to 350 degrees. Arrange the oven racks to the lower 1/3 and upper middle.
Place the broth, brown sugar and adobo sauce in a small bowl and whisk together until the sugar has dissolved.
In a very large (12-inch) nonstick skillet, heat the oil over medium-high. Brown the chicken on all sides in batches, a total of about 8 to 10 minutes per batch. Remove the chicken to a rimmed plate.
Next, saute the white onion until richly browned, about 8 minutes. Use a slotted spoon to remove the onion to a small bowl, leaving as much of the fat behind as possible. You're now ready to start assembling your packages.
Cut eight 17 x 18-inch pieces of aluminum foil. Set aside. Unfold the banana leaves, cut eight – 17-inch pieces choosing sections of the largest relatively unbroken leaves. Trim off the thin hard strip of the side of all the pieces. To make the pieces pliable, either steam them for 20 minutes or pass each one briefly over an open flame until it turns from dull and stiff to soft and shiny. Assemble the chicken packages as follows. One piece of foil, one piece of banana leaf, 3 to 4 slices of sweet potatoes, 2 to 3 pieces plantain, one piece of chicken, followed by a portion of the onions, and 4 to 5 strips of chipotles. Gather up the foil to create a boat shape, then drizzle 1/4 cup of the chicken broth mixture over the top. Wrap the banana leaf to completely cover the chicken, then fold the two long ends of the foil together to seal the top. Finally, fold up each end to create a sealed package. Transfer the chicken packages to 2 rimmed baking sheets and place in the oven. One sheet on the top rack and one on the lower rack. After 20 minutes, switch the baking sheets. Bake for an additional 25 minutes or until the chicken is cooked through.
Carefully open the foil packages and using a metal spatula, transfer the banana leaf package to a warm plate. Open up the leaf and fold it down to reveal the chicken. Drizzle any of the flavorful broth that is left in the foil over the top.
Jill's Wine Recommendation: I like to pair red chiles with red wine, so I think because of the sweeter flavors of the plantains, sweet potatoes, and brown sugar I would use a Zinfandel. The spicy, rich fruit of the 2008 Easton Zin from Amador County, CA will make a great match.