Preheat the oven to 350°F. Lightly coat a 9 x 13-inch baking dish with nonstick cooking spray.
In a large mixing bowl, combine the green enchilada sauce, sour cream, about 1/4 cup mayonnaise, Tajín to taste, and a couple of handfuls of shredded Monterey Jack.
Add the drained Mexican-style street corn. Chop the rotisserie chicken into smaller pieces, add it to the bowl, and stir until everything is evenly combined.
Cut a stack of mini corn tortillas into quarters. Arrange enough tortilla pieces to cover the bottom of the prepared baking dish. The layer does not need to be perfect.
Spread all of the chicken and street-corn mixture over the tortilla layer. Top with another layer of quartered corn tortillas.
Reuse the mixing bowl for the topping. Add the Southwest-style corn, the remaining Monterey Jack, a few more tablespoons of mayonnaise, and another sprinkle of Tajín. Stir to combine.
Spread the corn-and-cheese mixture evenly over the top tortilla layer.
Cover the baking dish tightly with aluminum foil. Bake at 350°F for about 20 minutes.
Remove the foil and bake for another 10 to 15 minutes, until the casserole is hot and bubbly and the cheese is melted. For extra browning, broil briefly at the end if desired, watching it closely the entire time.
Let the casserole rest for a few minutes before serving. Sprinkle with parsley if desired. If checking with an instant-read thermometer, the center should reach 165°F.