Oils are liquid fats. They are derived from plant sources (seeds, nuts, that sort of thing) and like animal fats have been in use by human beings for thousands of years. Speaking generally, they’re used more by cooks than bakers — solid fats are where it’s at for pastry types — but come in quite handy from time to time.

In the pastry kitchen oils are most valuable when they bring little-to-no flavor to the party. Though a walnut or a sesame oil might occasionally be used specifically for its flavor, most of the time pastry makers use oil solely to introduce richness and/or a moist texture into a cake or muffin formula. The same goes for frying, where the aroma of, say, peanuts or corn can muddle the profile of a fritter or a doughnut.