Cook macaroni until al dente, according to package directions, about 7 minutes. Drain well.

While pasta is cooking, warm milk until steamy but not boiling.

In another medium-sized saucepan, melt butter. Add flour, and whisk until smooth.

Add warm milk to butter/flour mixture. Whisk until smooth.

Cook, stirring constantly, on low heat for 2 minutes.

Add 4 cups shredded cheddar. Stir well, and then remove from heat. Set aside.

Stir salt,pepper, mustard, minced garlic or garlic powder, and chopped onions or onion powder into creamy sauce.

Place cooked macaroni in large mixing bowl.

Stir in cheese sauce.

Transfer mixture to greased 9x13 baking dish

Sprinkle with cornflakes, and then remaining shredded cheddar.

Bake at 400 for 10-12 minutes, or until hot and bubbly.