In skillet brown ground beef; drain off fat.
Stir in drained beans, enchilada sauce, tomato sauce, the 1 cup shredded cheese, and instant minced onion.
Set aside 1 cup of the corn chips; coarsely crush remaining chips.
Stir crushed chips into meat mixture.
Turn into a 1 1/2-quart casserole.
Bake, covered, at 375° for 30 minutes.
Spoon sour cream atop casserole; sprinkle with the 1/2 cup cheese.
Sprinkle reserved chips around edge of casserole.
Bake, uncovered, 2 to 3 minutes.