Preheat oven to 375 degrees F. Grease 9×13 casserole dish.
Heat up a medium saucepan until hot. Add oil and then sauté chopped onion for 5-6 minutes. Add minced garlic and cook until fragrant.
Add Ortega black beans, Green Giant corn, Ortega diced green chiles, 1 cup of black olives (reserve the other 1/2 cup), and sprinkle Ortega taco seasoning packet over pan and stir to combine.
Add diced tomatoes with green chilis, tomato sauce and chicken broth to pan. Stir and simmer for 12 minutes.
Scoop out some of the sauce, enough to cover the bottom of the casserole dish and layer three tortillas on top. Then layer with some shredded chicken, more sauce, then cheese. Repeat process until you’ve used all tortillas.
Top last layer with cheese and cover with foil. Place in oven and let bake for 30 minutes.
Bake uncovered for an additional 10 minutes or until cheese is melted to your desire. Top with the rest of the sliced black olives and chopped scallions.