It's important to make sure that the cooking oil reaches and maintains the correct temperature during the frying process. Oil that is not hot enough results in greasy or soggy donuts. Oil that is too hot will give you donuts that are cooked on the outside, but undercooked on the inside. Make sure you use a thermometer to monitor the oil temperature, and adjust the burner as necessary. (Click here for our instructions on calibrating your thermometer!) Only fry a few donuts at a time, and avoid overcrowding the pan, which can impact the oil temperature.