In a heavy cast iron pot or Dutch oven, heat the sesame oil over a fire. Rub the pieces of duck with the salt and pepper, and then brown them in the hot sesame oil until they have a rich, brown color. Remove the pieces of duck and set aside in a warm place. Saute the onion, sesame seeds, chile pasilla, chile ancho and poblano chile in the same pot until the chiles are tender. Add the chicken broth, chocolate, pineapple, bread, crushed plantain, garlic, peanut butter and sugar. Scrape the seed from the vanilla bean into the mixture. Bring the mixture to a boil and the decrease the heat to a simmer by moving the pot to the side of the fire. Let the sauce simmer for 30 minutes. Remove from the heat and puree the mole -- do not seal the blender airtight while pureeing a hot liquid -- and then return it to the pot. Put the pieces of duck in the mole and simmer for 1 1/2 hours. Remove the duck from the mole and serve with the sauce on the side.