Before you start cooking, shred your cooked chicken and cut the corn tortillas into strips. Have all your spices, beans, and green chiles ready for quick assembly.
Heat olive oil in your skillet over medium heat. Add the diced onions, chili powder, cumin, and garlic powder. Sauté for about 3–4 minutes until the onions soften and the spices bloom.
Reduce the heat to medium. Stir in the shredded chicken, green chiles, and black beans. Pour in the green enchilada sauce, stirring until everything is well-coated.
Gently fold in the tortilla strips, ensuring each piece is coated in the sauce. This helps soak in all the flavors while softening slightly.
Sprinkle cheese generously across the top. Either cover and simmer on low until the cheese melts, or pop the skillet under a broiler for a few minutes for that golden, bubbly finish.
Top the skillet with your choice of garnishes like avocados, cilantro, or sour cream right before serving.