This sauce is renowned for its use of multiple ingredients - including chocolate. The flavour and depth comes from the different types of chili that is enhanced by espresso and chocolate.
In a large saucepan place the dried chilis inside and add water until the chilis are just covered. Bring to a boil and then lower to a simmer. Cover with a lid and let the chilis cook for 1 hour. While the chilis are cooking prepare a sheet pan with a few sheets of paper towel (to absorb water) on top. Once the chilis have cooked remove them from the saucepan and place them on sheet pan to dry. We want to absorb as much excess water as we can. Let them rest for about 30 minutes.
Set your oven on to broil HIGH or 400F. While the chilis dry, place the quartered onions on another cookie sheet lined with tin foil. Add the crushed (but still whole) garlic as well as the tomatoes (cut them in half place them face down). We want to roast these veggies so get them nice and brown - even blistered. We do not want them burnt. Depending on your oven temperature this can take anywhere from 15 - 30 minutes.
At this point you want to de-seed the chilis. This is where the heat comes from and we don't want the mole to be too spicy. Refer to the post to see how this is done. Place the de-seeded chilis as well as the charred veggies into a blender and set aside.
In a small saucepan, heat up one tablespoon of olive oil on medium heat. Add the raisins and stir for a minute before bringing it to low heat. Stir constantly allowing the raisins to swell up. This should only take a few minutes. Set aside to cool for a few moments before adding it to the blender.
To the blender, add the nuts, sugar and all the dried spices. Use a spatula to give the mixture a quick stir. Add the espresso, coffee extract and broth. Pulse the mixture until it is nice and blended. You may need to use you spatula to incorporate the ingredients in between pulses. Add the chocolate. Taste and adjust for salt or more chocolate. See post for more details on flavour profile.
Plug in your slow cooker and add the chicken breast inside. Sprinkle with salt and pepper. From here you will add ONLY half the mole mixture. The other half can be frozen in a freezer safe container for 3 months.
Cover and cook on low for 8 hours or on high for 4-6 hours. You can stir the mixture halfway through to ensure an even coating. Once the chicken is cooked, place the chicken on a cutting board and shred it.
Place large frying pan on medium high heat and place the chicken along with the mole sauce that is in the slow cooker inside. Heat the mole and chicken together so that the sauce becomes further embedded into the chicken. Whatever left over sauce can be used to coat the tacos. However I like adding all the sauce to the chicken and cooking it until it dries up.
To assemble, place a bit of the chicken on a tortilla and top with queso fresco and lime coleslaw. Buen aprevecho!
* you can also use peanuts if you'd like!
** if you do not have an espresso machine you can also use 3 tbsp coffee extract or 1 tbsp coffee liqueur like Khalua
*** start with 1/4 cup of chocolate and increase it to 1/2 cup if you want the mole to be a bit sweeter or if you need to combat some of the tartness
*** I just use a bag of these finely sliced veggies that I get from Superstore. You can check it out here. Otherwise, use any coleslaw type veggies just make sure they are thinly sliced!