Heat a large skillet over medium-high heat and add olive oil. Sear the chicken pieces for about 2 minutes on each side until golden brown.

Pour in the Mexican style beer or chicken broth, cover, and reduce the heat to a simmer. Let the chicken cook for 15-20 minutes until fully cooked through, reaching an internal temperature of 165°F. Shred the chicken using two forks.

In the same skillet, add diced onions and sliced poblano peppers. Sauté for about 5 minutes until soft and fragrant. Stir in minced garlic, ground cumin, and dried oregano; cook for an additional minute.

Add the shredded chicken back into the skillet with the sautéed vegetables. Mix in the tomatillo salsa and drained black beans, cooking for an additional 2-3 minutes on low heat to meld flavors.

Preheat your oven to 350°F. In an oven-safe dish, layer half of the chicken mixture, half of the tortillas, and half of the shredded white cheddar cheese. Repeat with remaining ingredients, topping with cheese.

Place the casserole in the preheated oven and broil for about 5 minutes or bake at 350°F for 15 minutes until the cheese is melted and bubbly. Watch closely to prevent burning.

Remove from the oven and let sit for a few minutes. Garnish with fresh chopped cilantro and serve hot with optional toppings.