First, prepare the chicken. Bring a large pot of water to a boil and slice chicken breast into pieces that are roughly the size of your palm. Boil until cooked through, about 10 to 12 minutes. Drain and shred chicken, then set aside.
In the meantime, prepare the rice. Bring 2 cups of water to a boil in a small saucepan, then stir in the rice. Cover and turn heat to low and steam until all the water has been absorbed and rice is fluffy, about 25 minutes.
Preheat oven to 350 degrees F. Add beans, onion, jalapeno, green chiles, shredded chicken, and cooked brown rice to a 9x13 baking dish and stir to combine.
Add lime juice, 1 cup of the enchilada sauce, and 1 cup of the shredded cheese to the casserole dish. Stir gently to combine, then flatten into the dish and smooth the top of the casserole with the back of a spoon.
Rip each tortilla into 8 equal triangles, then lay them in a single layer to cover the top of the casserole.
Top the casserole with the remaining 1 cup of enchilada sauce, spreading it out evenly. Sprinkle with the remaining 1 cup of shredded cheese.
Bake, uncovered, until the cheese is golden-brown and bubbly, about 30 minutes.
Optionally garnish with chopped fresh cilantro, then serve immediately.
Notes
Shredded chicken: You can use a rotisserie chicken in place of boiling and shredding chicken breast to make this recipe even easier. A three-pound rotisserie chicken should yield approximately the right amount for one batch of this casserole.Make ahead prep: You can make the chicken and rice ahead of time and store both ingredients in the fridge for up to 1 day before assembling your chicken enchilada casserole.Storing & reheating leftovers: Store leftovers in an airtight container in the fridge for up to 5 days. Reheat single servings in the microwave for about 2 minutes, stirring halfway through. (Tip: we love making this casserole in our OXO glass baking dish since it comes with a lid for easy storage - no need to transfer leftovers to a separate container!)