Combine greek yogurt/sour cream and jalapeño salsa in a bowl.
I like to use my immersion blender but simply stirring it with a spoon will work!
Set aside.
In a separate bowl add chicken, black beans, zucchini, taco seasoning and green onions.
Toss until everything is coated with the taco seasoning.
In an 11x7 baking dish spread a thin layer of the jalapeño salsa mixture.
Cover the bottom with half of the tortillas.
Layer with half of the chicken and black bean mixture.
Sprinkle 1/2 a cup of cheese overtop and then spread with 1/2 of the remaining jalapeño salsa mixture.
Repeat once more.
Bake for 35 minutes.
Serve warm.
Corn tortillas carry the structural burden in this casserole, requiring careful management of moisture so the dish sets properly rather than turning into a puree. Starch gelatinization occurs when tortillas absorb surrounding liquids during baking, but excess water from vegetables like zucchini and spinach undermines that process. Salt draws free water out of cubed zucchini through osmosis. Toss the zucchini with salt ten minutes before mixing and pat the pieces dry with a paper towel. This prevents excess liquid from pooling in the 11x7 baking dish. Dairy safety also matters when building the sauce base. Blending Greek yogurt or sour cream with jalapeño salsa creates a creamy binder. Keep the oven temperature at 350 degrees Fahrenheit to heat the dairy gently without breaking the emulsion. Higher heat causes yogurt and sour cream to curdle into grainy solids.
Avoiding Soggy Casseroles
Too much moisture remains the primary failure point when layering layered corn tortilla dishes. Drain canned black beans thoroughly in a fine-mesh sieve and shake them vigorously to remove surface starches that trap water. Tear the corn tortillas into silver-dollar-sized pieces to ensure they distribute evenly throughout the layers. This sizing prevents dense pockets of dry masa from forming next to overly saturated spots. Press each layer down lightly with a spatula to eliminate large air pockets before adding the mozzarella cheese.
Make-Ahead and Storage Mechanics
Assembled casseroles hold well in the refrigerator for up to twenty-four hours before baking. Cover the baking dish tightly with plastic wrap to prevent the exposed tortilla edges from drying out and cracking. Freezing unbaked casseroles changes the starch structure, causing the corn masa to crumble upon baking. Store baked leftovers in an airtight container for up to three days. Reheat individual portions in a 325-degree Fahrenheit oven for fifteen minutes to restore crispness to the edges.