not your typical mac'n'cheese casserole

Ingredients

• 2 tablespoons dry minced onion
• 1 stick margarine
• 1/2 cup all purpose flour
• 4 1/2 cups milk
• 1/2 pound american cheese cubed
• 2/3 cup bleu cheese crumbled
• 1 cup cheddar cheese shredded
• 1/4 package original velveeta cheese (1/2 pound)
• 1/2 teaspoon salt
• 1/4 teaspoon pepper (i used white pepper)
• 1/2 teaspoon dry mustard powder
• 1 pound favorite macaroni cooked and drained
• 1 tablespoon olive or if you prefer canola oil
• 1 package cheetos brand corn puffs (individual sized)