Line a large baking sheet with kitchen paper and set aside.
In a large bowl, whisk together the ricotta, sugar and eggs until combined. Whisk in the milk.
Sieve in the flour, baking powder and salt, then whisk again until combined.
Pour about 5cm of oil in a deep, wide pan — make sure it is deep enough that the oil comes no more than ⅓ up the sides of the pan — and place over a medium-high heat.
Once the oil is hot (it should sizzle if you add a little batter) start to add 1 tbsp scoops of the batter to the oil - work in batches, taking care not to overcrowd the pan. They don’t have to be the perfect shape, they are supposed to look a little rustic.
Fry for 2 minutes before carefully rolling them over using a spatula or slotted spoon. Continue to fry for another 2 minutes - or until golden brown. Remove from the pan using a slotted spoon and place on the prepared baking sheet to drain off any excess oil. Repeat until you have used all the remaining batter.
Mix together the caster sugar and cinnamon in a bowl. Add the still warm (but not too hot) sfingi and gently toss to coat.
Place onto a serving plate and enjoy!