Step 1
Remove the stems veins and seeds from the chiles (you might want to wear gloves when you do this). Heat the lard in a heavy skillet over medium heat. Add the chiles and cook and stir until the chiles are fragrant about 1 minute being careful not to burn them. Remove the chiles and place them in a large bowl.
Step 2
Stir in the onion and garlic and cook until the onion is soft and translucent about 5 minutes. Remove and add to the bowl with the chiles.
Step 3
Break the flour and corn tortillas into pieces and add them to the skillet. Toast on both sides turning often until golden brown about 3 minutes. Remove; add to the bowl.
Step 4
If needed melt a small amount of additional lard in the skillet. Add the plantain pieces to the skillet and cook and stir until lightly browned about 5 minutes. Remove plantain; add to the bowl.
Step 5
Stir the almonds and peanuts into the skillet and cook and stir until fragrant about 1 minute. Sprinkle in the sesame seeds and continue cooking until sesame seeds are lightly browned 15-30 seconds. Remove; add to the bowl.
Step 6
Warm the tomatoes over medium heat in the skillet until heated through about 5 minutes. Remove from heat. Break the chocolate into chunks and stir into the tomatoes until melted. Pour the chocolate and tomato mixture into the bowl with the chile mixture; stir to combine.
Step 7
Working in small batches puree the mixture in a blender until smooth adding a small amount of water if needed to make a smooth sauce.
Step 8
Place the chicken into a large Dutch oven; pour the sauce over the chicken. Cover and simmer over medium low heat until the chicken falls off the bone 2-3 hours.