Heat 1 tablespoon of oil in a large cast iron skillet over medium heat. Add the chicken pieces and cook, stirring occasionally, until browned on all sides but not fully cooked through, about 6-8 minutes. Transfer the chicken to a plate and set aside.

Heat the remaining 1 tablespoon of oil in the same skillet. Add the cubed sweet potato and cook, stirring occasionally, until it begins to brown and tenderize, about 12-14 minutes.

Add the minced garlic, chili powder, cumin, salt, paprika, oregano, black pepper, and crushed red pepper to the skillet. Cook for 30 seconds until fragrant. Stir in the corn, bell peppers, and half of the sliced green onions. Cook for 2 minutes.

Pour in the can of undrained Rotel tomatoes and 1 cup of the chicken stock. Return the browned chicken to the skillet and stir well to combine. Bring to a simmer and cook for 5 minutes.

In a small bowl, whisk together the cornstarch with 1 tablespoon of cold water to create a slurry. Pour the slurry into the simmering liquid in the skillet, then add the drained black beans and 1/4 cup of chopped cilantro. Cook, stirring gently, until the sauce has thickened and the beans are heated through, about 2-3 minutes. If the mixture seems too thick, stir in up to an additional 1/2 cup of chicken stock.

Position an oven rack in the upper third of the oven and set to broil. Sprinkle the shredded Monterey Jack cheese evenly over the top of the skillet. Broil until the cheese is completely melted, bubbly, and just beginning to turn golden in spots, about 2-3 minutes. Watch it carefully to prevent burning.

Carefully remove the skillet from the oven. Garnish with the remaining sliced green onions and extra chopped cilantro. Serve warm in bowls, topped with a spoonful of guacamole if desired.