For the Sauce:

15 tomatillos, husks removed

3 jalapeño peppers

4 cloves garlic

½ cup loosely packed cilantro leaves

¼ cup loosely packed green onions (green parts)

Up to 1½ cups chicken or vegetable broth (as needed)

½ cup sour cream

2 tablespoons olive oil

For the Casserole:

6 (8-inch) flour tortillas

1 pound boneless, skinless chicken breasts

1½ cups shredded cheese (Monterey Jack, mozzarella, or cheddar blend)

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Preheat the oven to 425°F (220°C) and line a baking sheet with foil.
Place tomatillos, jalapeños, and unpeeled garlic cloves on the sheet, drizzle with olive oil, and roast for 15–20 minutes until softened and slightly blistered.
Peel the garlic, then transfer all roasted vegetables to a blender. Add cilantro, green onions, sour cream, and 1 cup of broth. Blend until smooth, adding more broth as needed for desired consistency. Season with salt and pepper.
Cook the chicken breasts in a skillet with a bit of salt and pepper until fully cooked, then shred with two forks.
Reduce oven temperature to 375°F (190°C).
Spread a thin layer of tomatillo sauce on the bottom of a baking dish.
Layer two tortillas, followed by shredded chicken, a few spoonfuls of sauce, and a sprinkle of cheese.
Repeat the layers twice more, finishing with sauce and remaining cheese on top.
Bake uncovered for 20–25 minutes, until cheese is melted and bubbly with golden edges.
Let the casserole rest for 10 minutes before slicing and serving.

Use rotisserie chicken to save time.

For extra flavor, add sautéed onions or roasted corn between layers.

Leave jalapeño seeds in for more heat, or remove them for a milder sauce.

Make vegetarian by replacing chicken with black beans or roasted veggies.

Freeze up to 2 months and reheat after thawing overnight in the fridge.