This is the 11111th most frequent Korean word.
기름에
"기름에" means "in oil" or "with oil."
Here, "기름에" is used to indicate that the cooking method involves using oil as the medium.
고기를 기름에 구웠어요.
I cooked the meat in oil.
In this sentence, "기름에" is used to specify that frying is done with oil.
기름에 튀긴 음식은 바삭바삭해요.
Food fried in oil is crispy.
This usage of "기름에" denote the purpose of the oil as a styling aid for hair.