In 10-inch skillet, heat up the chopped meat, green onions, roasted corn, black beans, and salsa over medium-high heat, for 5 to 7 minutes, stirring occasionally until heated through. Salt and pepper to taste.
Add 2 cups of cheese to the meat mixture; gently mix.
Heat prepared or leftover mashed potatoes.
Prepare a 9×13 pan with cooking spray. Spoon the hot meat mixture into the pan. Sprinkle with remaining 1 cup of cheese. Cover (spread) the top with heated, prepared mashed potatoes.