Preheat oven and poach the chicken: Preheat the oven to 375°F (190°C). Place the chicken breasts in a medium saucepan and cover with about 1 inch of water or low-sodium chicken broth; add 1/2 teaspoon salt and a couple of peppercorns if you have them. Bring to a gentle simmer over medium heat, then reduce to low and simmer for 12–14 minutes until the thickest part registers 160°F (71°C). Why: poaching keeps the chicken moist and tender and produces a flavorful cooking liquid you can use to moisten the casserole.

Shred the chicken: Remove the chicken to a cutting board, let rest 5 minutes, then shred with two forks or chop into 1/2-inch pieces. Reserve 1/2 cup of the poaching liquid and discard the rest. Why: shredding while warm yields soft threads of meat that mix evenly into the filling; reserved liquid will add moisture and flavor without watering down the casserole.

Sauté the aromatics and vegetables: In a large skillet heat the olive oil over medium-high heat until shimmering. Add the chopped onion and a pinch of salt and sweat for 3–4 minutes until translucent—don’t brown. Add the garlic and cook 30 seconds until fragrant (this blooms the garlic’s aromatics). Add the diced red and green bell peppers and cook 3–4 minutes until slightly softened. Why: cooking the vegetables first develops their flavor and reduces water release in the casserole so it doesn’t get soggy.

Toast the spices and combine: Push the vegetables to the side of the pan and add the cumin, smoked paprika and chili powder to the hot oil for 20–30 seconds until aromatic—this wakes up the ground spices and deepens their flavor. Stir everything together and add the corn and drained black beans. Cook for 1–2 minutes to warm through.

Build the saucy filling: Stir in the salsa, reserved 1/2 cup chicken poaching liquid, chicken broth, lime juice, 1/2 teaspoon salt and the shredded chicken. Simmer gently for 3–4 minutes to let flavors marry and thicken slightly. Taste and adjust seasoning with more salt, pepper or lime as needed. Why: simmering briefly concentrates the salsa and melds the ingredients so every spoonful is cohesive rather than watery.

Prepare the casserole base and layer: Lightly oil a 9x13-inch (23x33 cm) baking dish. Scatter half of the torn corn tortilla pieces evenly across the bottom—these will soften and form a chewy, slightly crisp base after baking. Spoon half of the chicken-vegetable filling over the tortillas, then sprinkle 1 cup of shredded cheddar. Repeat with the remaining tortillas, filling, and finish with the remaining 1 cup cheese on top. Why: layering tortillas inside the dish creates texture and absorbs the savory liquid so you get soft, tortilla pockets with a golden cheese finish.

Bake until bubbly and golden: Tent the dish loosely with foil and bake at 375°F (190°C) for 20 minutes. Remove the foil and bake another 10–12 minutes until the cheese is melted, edges bubble and the top has light golden spots. Let rest 8–10 minutes before serving. Why: resting lets the casserole set so it slices cleanly and gives the tortillas time to finish absorbing juices.

Finish and serve: Garnish with chopped cilantro and an optional squeeze of lime. Serve with sour cream, sliced avocado or pickled jalapeños on the side. Why: fresh cilantro and lime brighten the rich cheese and chicken and cut through the dish’s richness.