Cut a circle into the middle of the doughnut. Shot glasses or water bottle lids work great.

Place the doughnuts into hot oil until they turn golden brown. 

I had to watch how hot the oil was after my first couple of doughnuts. They started to turn brown really quickly and still be soft on the inside

I sprinkled cinnamon and sugar on the doughnuts and served them hot. They also tasted great with powdered sugar on them.