Okay, so I attempted doughnuts last night, using a properly calibrated thermometer, a cast iron dutch oven and an electric stove. The recipe is one that I have used previously, in a different pan, with a different thermometer, and on a gas stove, and it worked fine then. Last night, however, it was a complete disaster, with the doughnuts burning on the outside and totally raw on the inside. I've only made doughnuts a couple of times previously, and I'm not super knowledgeable about deep-frying in general, especially not on an electric stove. The temperature kept spiking wildly every time I added a doughnut to the oil, which didn't make sense to me, since I thought the oil was supposed to cool when I added the doughnuts.
So, in short, I'm asking for any tips regarding doughnuts (and deep-frying in general) on an electric stove, and any enlightenment as to what could have gone wrong?