Step 1

Bring 8 cups water and 1/2 tablespoon salt to a boil in a large stockpot over high. Reduce heat to medium-low, and add chicken. Cook until chicken is tender and a thermometer inserted in thickest portion of meat registers 155°F, about 30 minutes. Remove chicken; set aside on a large plate. Reserve 4 cups chicken cooking liquid in a large heatproof bowl; discard remaining cooking liquid.

Step 2

Heat 1/4 cup vegetable oil in a 12-inch skillet over medium-high. Add 8 garlic cloves; cook, stirring constantly, until fragrant, about 1 minute. Add tomatoes, onions, and 1/2 tablespoon salt; cook, stirring occasionally, until onions are translucent and softened, about 8 minutes. Transfer mixture to a blender. Secure lid on blender, and remove center piece to allow steam to escape. Place a kitchen towel over opening in lid. Process until smooth, about 1 minute. Transfer mixture to a large bowl, and set aside.

Step 3

Wipe skillet clean. Add 3 cups vegetable oil; heat over medium-high. Working with a few different types of chiles at a time, place in a spider, and submerge in hot oil for 2 seconds per batch. Remove from oil using spider, and place in a large heat-proof bowl. Repeat with remaining chiles and remaining 4 garlic cloves.

Step 4

Place sesame seeds and pepitas in a medium metal strainer; submerge in hot oil in skillet over medium-high. Cook, stirring mixture inside strainer and shaking occasionally, until seeds are golden brown and fragrant, about 2 minutes. Transfer seed mixture to bowl with Chile mixture.

Step 5

Working with 1 tortilla at a time, add to hot oil in skillet over medium-high. Cook, turning occasionally, until golden brown, 30 seconds to 1 minute. Transfer fried tortillas to a plate lined with paper towels; let cool 5 minutes. Break into 2-inch pieces. (Strained and cooled oil may be reused for frying.)

Step 6

Add chile mixture, tortilla pieces, and bolillo pieces to reserved 4 cups chicken cooking liquid in bowl. Let stand until liquid is almost absorbed and bolillo has softened, about 10 minutes. Transfer mixture to a blender; process until smooth, about 1 minute.

Step 7

Heat remaining 1/2 cup vegetable oil in a large pot over medium. Add tomato mixture; cook, stirring constantly, until heated through, about 1 minute. Add blended chile mixture and chocolate disk. Bring to a simmer over medium-high. Cook, stirring occasionally, until chocolate has melted and mixture is well combined, about 20 minutes. Add cooked chicken and remaining 1 tablespoon salt; stir to submerge in mole. Reduce heat to medium-low; cover and simmer until chicken is heated through, 10 to 15 minutes. Serve with rice and tortillas, and garnish with additional sesame seeds.