Preheat oven to 350° F.  Grease an oven safe 10×10-inch dish. Set aside.

Bring 1 quart water to a rapid boil over medium heat. Add potato slices and boil for 5 minutes. Add onion slices during the last minute of the boil.  Drain and set aside.

Whisk together Campbell’s® Cream of Mushroom Soup, milk, garlic powder and pepper in a medium bowl.

Spoon ¼ cup soup mixture on dish surface and spread into a thin layer. Layer half the potato/onion mixture, half the chorizo mixture, half the soup mixture and half the cheese over  the thin layer of soup mixture.  Repeat layers ending with cheese. 

Bake for 60 minutes or until cooked through and cheese is completely melted.