Which cooking method involves immersing food in hot oil?

The cooking method that involves immersing food in hot oil is frying. This technique can be further categorized into deep frying, where the food is completely submerged in hot oil, and shallow frying, where only a small amount of oil is used. Frying allows food to develop a crispy texture and golden-brown color on the outside while cooking through on the inside, which is a hallmark of this method. The high temperatures of the oil also help to quickly seal the surface of the food, locking in moisture and flavor.

In contrast, poaching involves gently cooking food in simmering water or broth without the use of oil, while boiling is the process of cooking food in water or other liquids at high temperatures. Searing refers to browning the surface of food quickly at high heat, typically in a skillet, but does not involve immersing the food in oil like frying does. Thus, frying is definitively the method that matches the description provided in the question.