Make chile purée: Preheat oven to 300°. Lay dried chiles in a single layer in 1 or 2 rimmed baking sheets. Bake until fragrant and flexible, about 5 minutes. While warm, discard stems, open up, and shake out and discard loose seeds.
Rinse chiles, put in a large bowl, and add 2 qts. boiling water. Let stand until soft, 20 to 30 minutes. Drain, reserving chile liquid. Purée half of chiles at a time in a food processor (including canned chipotle) with 1 cup chile liquid per batch. Pour through a fine strainer into a large bowl, pressing firmly with a spoon; discard residue. Set aside.
Roast vegetables: Preheat oven to 450°. Lay vegetables and tortillas in a single layer in a rimmed baking pan. Bake, turning occasionally, until ingredients have dark brown spots or edges, 15 to 25 minutes; remove as done. Let cool.
Squeeze garlic from skins. Pull off and discard tomato skin. Purée ingredients in food processor, gradually adding 1 cup reserved chile liquid. Pour through fine strainer into bowl with chile purée, pressing firmly with a spoon. Set aside.
Cook seasonings and thickeners: In a large frying pan over medium heat, toast 1/2 cup sesame seeds, stirring often, until golden, 3 to 4 minutes. Transfer to a bowl. (Toast extra seeds for serving now and set aside.) To pan, add oil and remaining seasonings and thickeners. Cook, stirring often over medium heat, until richly browned, 7 to 10 minutes.
On a work surface, pound cinnamon sticks a few times with a mallet to break up. Purée with plantain mixture and sesame seeds in a food processor, gradually adding remaining chile liquid (blending will take several minutes). Pour through fine strainer into bowl with chile purée, pressing firmly with a spoon.
Assemble mole: In a 6- to 8-qt. pot, combine chile mixture and 2 cups chicken broth. Cover and bring to simmering over medium heat. Reduce heat and simmer to blend flavors, stirring often, about 2 hours. Stir chopped chocolate into sauce.
Thin mole with more chicken broth if needed so sauce is pourable. Season to taste with salt and return to simmering. Arrange turkey in a large, shallow serving dish. Spoon about 10 cups mole over meat. Scatter sesame seeds, cilantro, and chopped onion on top. Serve in wide bowls with lime wedges and tortillas.
*Package labeling can be confusing; true mulato and ancho chiles are both dried poblanos but slightly different varieties (the mulato is hotter). Both have wide shoulders, while pasillas (dried chilaca chiles) are long and skinny. Find them at well-stocked Latino markets and at worldspice.com. For turkey, simmer 2 breast halves (with bones and skin, 5 to 6 lbs. total) in a pot of salted, simmering water until 165° in thickest part, 35 to 40 minutes.
MAKE AHEAD The mole, through step 7, up to 4 days, chilled; reheat to simmering, stirring often.