NOTE 1: As a rule of thumb, you need enough oil so that your food can be kept as separated as possible while cooking, and so that it can be kept fully covered by oil. Overcrowding of a deep-fryer will result in a nothing more than a soggy mess! The oil should be smoking hot before the food is added. A handy test for correct temperature is to toss in a bread cube. It should be a golden color after 30 seconds.
NOTE 2: Once you have enough cooked onions, turn off the oil. The onions in buttermilk will save if refrigerated.