Heat oil in a large heavy pot and attached a deep fry thermometer to the side. Heat the oil to 365ºF/185ºC.
In bowl whisk the flour, baking powder and salt.
In another bowl, whisk the ricotta, eggs and superfine sugar until smooth.
Gradually whisk the milk into the ricotta mixture and then the vanilla.
Gently whisk the ricotta mixture into the flour until combined.
Before you start frying mix the sugar and cinnamon (if using) in a bowl ready to roll the sfingi.
Prepare a tray lined with paper towels ready to drain the sfingi.
Once the oil is at the correct temperature, use two teaspoons to scoop and push the batter into the hot oil. Don't overcrowd the pan. Fry for about 5 minutes until the sfingi are well browned.
Remove and drain on the paper towels then roll in cinnamon sugar