Butter and olive oil are both fats but differ clearly. Butter consists of around 80 per cent fat, the rest is mainly water. Its fat is mostly saturated. Olive oil is pure fat and consists mainly of monounsaturated oleic acid.
In many recipes butter is easy to replace: for frying, over vegetables, in mashed potatoes or on bread. For baking, use about three quarters of the amount of butter. Only where butter needs to stay solid, as in puff pastry, is olive oil not a good choice.
