Many recipes begin by heating oil in a pan, then adding other ingredients. But there are plenty of exceptions that call for starting with cold oil. On Milk Street Radio, Jessica Keahey of Fayetteville, Arkansas, recently asked why it matters and when each approach is best.

The answer requires an understanding of the different roles oil can play. In many cases, hot oil—generally the result of adding oil to a pan, then heating it until shimmering or barely smoking—can be nothing more than a visual cue that the pan is sufficiently hot. This is because a hot pan is crucial for properly searing and sautéing, and must be at temperature before the food is added. (See here for a handy chart that lists the smoke point of common cooking oils, from grapeseed oil to olive oil. The smoke point is the temperature at which the oil starts to break down and smoke.)

But hot oil can also serve a role in preventing sticking; it can instantly cook the surface of an ingredient—steaks or eggs, for example—before it makes contact with the pan.

There are times, however, when a slower, gentler approach is best. A cold pan and cold oil are the way to go when cooking items that easily burn, such as fresh herbs and spices (see this recipe for spiced butter popcorn). Cold oil is also best for drawing out fuller flavor, as when sweating aromatics. This is especially true for all members of the garlic and onion family, which release flavorful enzymes when chopped or sliced. Those enzymes are deactivated by heat, which means adding them to hot oil will quickly dull their flavor.

So as a general rule, heat your oil when you need a quick sear or worry that ingredients might stick, but start cold when working with delicate foods or creating more nuanced flavor.