Frying is, as everybody knows, cooking in boiling fat, this fat being, according to taste, traditions and circumstances, beef fat, lard or oil. Butter is no use for frying, as it burns before it reaches the high temperature required for good frying. Also, the thing you want to fry must contain a great deal of starch, potatoes being the perfect example of an aliment which fries well naturally. It therefore stands to reason that, if you wish to fry something which is not of a starchy nature, you have to prepare it, either by painting it with beaten egg and breadcrumbs (escalopes viennoise, fish) or by dipping it in a special batter (apples, salsify, etc.), in the shape of fritters.