Whisk together the milk, sugar and yeast and leave to foam up, roughly 5 minutes.
Mix in the flour, eggs, butter, sugar and salt. Mix to a wet batter and turn out onto a well floured board.
Work the dough, bringing in enough flour to make it not too sticky. Leave to rise for an hour.
Roll out the dough to roughly 2 cm thick. Use a cookie cutter to cut small circles from the dough. Set them all on a floured tray and leave to rise for another half an hour.
Meanwhile, cut the caramel chocolate bars into pieces and freeze for roughly an hour.
Take each circle of dough and press a piece of frozen chocolate inside. Pinch up the sides to seal tightly - use a splash of water to help stick if necessary, otherwise they'll puff up and the chocolate will escape during frying.
Heat the oil to 160°C/320°F.
Fry the doughnuts in batches, flipping every now and then, until they've puffed up and gone a deep golden brown.
Use a slotted spoon to take them out of the oil and set them on some towels to soak up most of the oil. Toss them in the granulated sugar.