In a small bowl, mix sweet potatoes, duck and chipotle pepper to make filling. Choosing largest ones, place corn husks, one at a time, on work surface and spread 1/4 to 1/3 cup tamale dough over wide end of husk; top with a tablespoon of duck filling. Fold husk around tamale filling to completely enclose, and tie off each end with a strip of corn husk. Repeat until all dough and filling has been used.
In a large pot fitted with a steaming rack, arrange tamales and cover with remaining soaked corn husks or a damp dish towel. Pour in enough boiling water to reach just under steaming rack, cover tightly and return to a boil over high heat. Reduce heat slightly to maintain gentle bubbling and steam. Cook about 1 hour, adding more boiling water if necessary, until tamales are cooked through. Uncover pot and let tamales rest 10 minutes before serving.
Yield: 12 servings