||Heat the oil in a skillet set over medium-high heat. Once hot, add the onion and cook for 4 to 5 minutes, until wilted. Add the garlic, and cook for a minute, until fragrant. Add the nopalitos and cook for 2 to 3 minutes, until their color transforms. Incorporate the poblano chile rajas, season with salt and pepper to taste and continue cooking for a minute or two, set aside. Heat the tortillas.
||Spread ¼ of the Salsa on the bottom of a 9-by-13-inch baking dish. Cover with a layer of tortillas. Top with half of the cooked chicken, half of the poblanos mixture and one-third of the cream and melty cheese. Top with a layer of tortillas. Top with the black beans and corn and ¼ of the Salsa. Top with a layer of tortillas, add the rest of the chicken, and poblanos mixture along with the remaining sauce; and the remaining cream, Cotija, and melty cheese.
||Cover the casserole dish with aluminum foil. Bake for 25 minutes, remove the foil and bake for another 15 to 20 minutes or until the top is bubbly and the cheese has melted. Serve hot. Serve the training sauce to be served on the side.