The biggest difference between butter and oil when it comes to deep frying is that butter is a dairy product, not a liquid fat like oil. Butter is composed of about 80 percent fat, 16 percent water and 4 percent milk solids. The milk solids are the problem; they start to burn and smoke when they get too hot. Unfortunately, the optimum temperature for frying is the same as butter's "smoke point."

Butter's smoke point is 350 degrees Fahrenheit, which is the same temperature at which food should be fried in a deep-fryer. The smoke point is the temperature at which a fat starts to burn and smoke, and each type of fat has a different smoke point. A fat's smoke point depends on its percentage of free fatty acids and the amount of impurities it contains. This is why light olive oil, a more refined version, is better for frying than extra virgin olive oil, a purer form of the oil with a lower smoke point. Compared to butter, two recommended deep-frying oils, vegetable and peanut, share a smoke point at 450 F. That 100-degree difference between frying's optimum temperature and the smoke point of the best frying oils makes for successful cooking.

Some authorities have suggested that it's possible to combine butter with oil to raise butter's smoke point and get buttery flavor in fried foods. The problem with this idea is those savory, pesky milk solids. They're not fats, so they won't melt together with the oil; they'll separate, burn and smoke just as vigorously as if butter were the only fat. The sad result will be a burnt carbon flavor to the chicken that's the complete opposite of the desired result.

Getting buttery-flavored fried chicken might be accomplished in three ways. For one, it's possible to cook boneless, skinless chicken breasts in butter, provided the temperature is kept below the 350 F frying point. Another option is to soak the chicken pieces in buttermilk prior to dredging them in flour for frying. The liquid left after butter is churned, buttermilk contains tiny flecks of the milk solids that give butter its flavor. Buttermilk can give fried chicken a savory tang with a hint of buttery taste. A third option is for diners to put butter on hot fried chicken after it's served. These options would work better than trying to make butter adapt to deep-frying, a use for which it's really not suited.