Butter: Gives the sauce rich flavor. Flour: Thickens the sauce. Milk: Thins the sauce out a bit and adds sweet flavor. Sharp cheddar cheese: Freshly grated cheese will melt better and give a stronger flavor than the coated shredded cheese you can buy in a bag at the store.
Other common additions to help offset the lack of flavour in poorly-aged cheeses are:Salt. Remember, salt is essentially a flavour enhancer and will bring out the natural taste of any other ingredient.Mustard. Ground cayenne or red pepper.