Heat a large cast-iron skillet or comal over medium-high. Add chiles in 3 batches; cook each batch until toasted, blistered, and darkened in color, 1 to 2 minutes. Transfer chiles to a heatproof bowl; pour boiling water over to cover chiles. Let soak, covered, until softened, about 15 minutes. Drain chiles; discard soaking liquid. Transfer to a blender with 1 ½ cups water. Blend until smooth, adding more water as needed. Transfer to a medium bowl; set aside.

While chiles soak, return skillet or comal to medium heat. Add 2 tablespoons of the oil, and swirl to coat. Add raisins, pumpkin seeds, peanuts, pecans, and almonds; cook, stirring often, until toasted and fragrant, 3 to 4 minutes. Transfer with a slotted spoon to a heatproof bowl; set aside to cool slightly.

Tear tortillas and bread into 2-inch pieces. Without wiping out skillet, add tortilla and bread pieces; cook over medium, stirring once or twice, until toasted and lightly browned, about 2 minutes. Transfer to bowl with nut mixture.

Add coriander seeds, anise seeds, peppercorns, cloves, canela pieces, reserved chile seeds (if using), and ½ cup of the sesame seeds to skillet; cook over medium, stirring often, until toasted and fragrant, about 2 minutes. Transfer to a spice grinder and grind to a fine powder; set aside.

Return skillet to medium-high, and add 2 more tablespoons of the oil; swirl to coat. Add onion slices; cook, stirring occasionally, until browned and starting to soften, about 6 minutes. Add tomatoes, tomatillos, and garlic; cook, stirring occasionally, until all vegetables are soft and browned in spots, about 10 minutes. Transfer to blender with ground spices and toasted nut mixture. Blend, adding up to 1 cup of water as needed, until smooth, about 2 minutes.

Heat remaining 3 tablespoons oil in a Dutch oven or cazuela over medium. Add chile puree; cook, stirring often, until it darkens in color and is very thick, about 10 minutes. Whisk in pureed vegetable mixture until incorporated and smooth; reduce heat to a simmer, and cook, partially covered, stirring occasionally, until mole thickens, about 20 minutes.

Add 2 cups of water; continue cooking until mole coats the back of a spoon, 1 to 1 ½ hours.

Add chocolate pieces; cook, stirring often, until melted, about 5 minutes. Stir in sugar and salt. Garnish with remaining ¼ cup sesame seeds, and serve with warm corn tortillas.