My wife was making donuts in a parve pot. The pot was filled with a couple of inches of hot oil. My wife mistakenly put a donut stuffed with milk chocolate into the oil. It is debatable weather or not there was 60 times oil to chocolate ratio (definitely not 60 oil to donut ratio) I assume if I want to keep the parve status of the pot I need to kasher.
Being that oil gets hotter than water can I kasher with water?
Do I need libun?
Interesting point. The poskim discuss your question, and they say that that chazal determined that the heat of boiling water will take out taste even if was absorbed thru cooking at a higher temperature. For example, koshering a pressure cooker, where the temperature gets hotter than a regular pot, or when the food was cooked with oil which gets hotter than water. Therefore, all you need is that the water should be boiling.
Regarding your specific situation, if there was 60 times the chocolate in the dough of the donut plus the oil you would not need to kasher the pot.
To add to this, in general, there is no need to do libbun since the absorbed taste was not one of issur, since it was only milchig and pareve. Therefore, even if you would have fried the doughnuts in a minimum of oil, you would still be allowed to do hagala on the pot. Additionally, in general we only do hagala with water and not with other liquids.
See B’tzel Hachochma 3-55, and Moadim U’zmanim 4-281.
O:CH 451-5, Shach Y:D 121-8, Pischei Teshuva ibid 7, Rema Y:D 121-5.