Delicious! I used Mexican cheese blend in place of the cheeses listed.
Delicious! I used Mexican cheese blend in place of the cheeses listed.
Swapping corn tortillas for flour alters the final bake significantly, as flour varieties absorb significantly more moisture from the surrounding sauce and turn pasty during a one-hour bake. Sticking to corn maintains structural integrity, though cold corn tortillas will crack immediately upon rolling. Soften them first by steaming them in a damp towel for one minute or passing them quickly through hot oil in a skillet.
The primary error cooks make with this style of casserole involves moisture control. Condensed cream soups combined with a full pint of sour cream create a heavy dairy blanket. If the oven temperature drifts above 375 degrees Fahrenheit, the dairy solids separate and break, resulting in an oily pool atop the baking dish rather than a smooth sauce. Keep the oven calibrated accurately.
Muenster and Colby longhorn melt into a stretchy blanket, but grating pre-bagged cheese introduces anti-caking starches that ruin the creamy mouthfeel. Shred blocks by hand. Cover the 9x13 inch baking dish loosely with foil for the first thirty minutes of baking to prevent the edges from scorching, then remove the foil to let the cheese brown properly.