1. Heat oven to 425 degrees F. Bring water and salt to boil in a large saucepan. Reserve 2 tablespoons instant polenta. Gradually whisk remaining polenta into boiling water. Reduce heat to low; cook, stirring, 5 minutes. Reserve 1/4 cup cheddar cheese. Stir remaining cheese into polenta.
2. Meanwhile, brown beef in large skillet over high heat. Drain fat from skillet and discard. Stir in beans, tomato sauce, corn, chiles, green onions and reserved polenta; heat through.
3. Spoon beef mixture into a shallow 2-quart casserole. Spoon polenta over top. Sprinkle with reserved cheddar. Place casserole on a jelly-roll pan. Bake 20 minutes or until top of pie begins to brown. Makes 6 servings.