Which cooking method involves using heated fat to cook food?

Frying is the cooking method that involves using heated fat to cook food. This technique relies on the application of hot oil or fat, which cooks the food by surrounding it and transferring heat. As the food is submerged or in contact with the hot fat, it undergoes a process of crisping and browning, resulting in a distinct flavor and texture that is characteristic of fried foods.

The other options represent different cooking methods: steaming uses water vapor to cook food, baking employs dry heat in an oven, and boiling involves cooking food in water or broth at high temperatures. Each of these methods has its unique culinary applications and effects on food, but they do not utilize fat as a primary cooking medium like frying does.