Preheat the oven to 400 degrees F.Heat a large oven safe skillet over high heat. Add the tomatillos and cook, turning often until they begin to char and become soft. Remove from the skillet. Let cool and then give them a rough chop.Return the skillet to medium heat and add the olive oil and onion. Cook for 5 minutes or until the onion is fragrant. Stir the chopped tomatillos, green chiles, and chipotle chiles and cook another minute. Add the tomatoes, beer, oregano, bay leaves, and salt. Bring to a simmer over medium heat. Slide the chicken into sauce and cook for 15 minutes or until the chicken is cooked through and the sauce has thickened slightly. Remove from the heat. Discard the bay leaves and shred the chicken in the skillet. Stir in the cilantro. Lay the corn tortillas flat over the chicken. Add the cheese in an even layer, transfer to the oven and bake for 10-15 minutes or until the cheese has melted. Serve topped with cilantro, and avocado, if desired. EAT.