Whisk together the flour, egg and milk in a bowl to form a smooth batter. Add the Stilton and mix well.
Heat 1cm/½in depth of vegetable oil in a deep frying pan. (CAUTION: hot oil can be dangerous. Do not leave unattended.)
Dip the apple into the batter and lower into the hot oil. Shallow fry the fritters until the batter is crisp and golden.
Drain onto kitchen paper, dust with cinnamon and serve warm on plates.