Heat a large, deep skillet over medium-high heat. Add the ground beef and cook for 6–8 minutes, breaking it into uniform crumbles, until deep golden brown. Fully drain any excess pooled fat to keep your sauce from separating into an oily layer during the bake.

Stir the taco seasoning mix directly into the warm beef. Let the dry spices coat the hot meat for 2 minutes to cook off the raw spice taste and bloom the aromatics.

Reduce the heat to medium-low. Add the mild enchilada sauce, diced green chilis, drained corn, and the can of refried beans directly to the skillet.

Whisk or stir vigorously for 5 minutes until the smooth refried beans melt completely into the enchilada sauce. Pro Tip: This creates a dense, starch-thickened meat gravy that prevents the casserole from turning watery or running all over the plate when sliced.

Lay 4 of the halved flour tortillas across the bottom of a well-greased 9×13-inch baking dish, overlapping the straight cut edges slightly to create a completely solid, gap-free foundation. This "tortilla armor" prevents the bottom of the casserole from baking directly onto the glass.

Evenly spread exactly half of the hot bean-and-meat gravy over the tortilla base, then blanket it with 1 cup of the taco cheese blend.

Place the remaining 4 halved tortillas on top of the cheese layer. Pour the remaining half of the meat mixture over the top and scatter the final cup of cheese over everything. Bake at 350°F for 20 minutes until the cheese is entirely liquefied and bubbling at the perimeter. Top with fresh green onions immediately upon removal from the oven.