Begin by heating the olive oil in a large skillet over medium heat. Once hot, add the finely chopped onion and sauté for about 3-4 minutes until the onion is translucent and fragrant.
In a mixing bowl, combine the cooked quinoa, shredded chicken, black beans, green chiles, and enchilada sauce. Once the onion is ready, add it to the bowl and mix everything thoroughly until well combined.
Preheat your oven to 350°F (175°C). In a baking dish, spread half of the quinoa mixture evenly across the bottom. Top this layer with half of the shredded cheddar and mozzarella cheese. Then, add the remaining quinoa mixture on top, finishing with the rest of the cheese.
Cover the baking dish with aluminum foil and place it in the preheated oven. Bake for 25 minutes covered, then remove the foil and bake for an additional 10-15 minutes, or until the cheese is bubbly and golden brown.
Once baked, remove the casserole from the oven and let it cool for a few minutes. Serve hot, garnished with a dollop of sour cream, a sprinkle of freshly chopped cilantro, and lime wedges on the side for that perfect zesty touch.
