In a mixing bowl, add the grated cheeses (feta, graviera, gouda), the eggs, and the milk. Combine the mixture well and season with pepper and paprika. Add in some bread crumbs, if the mixture looks too runny.
Cover the bowl with plastic wrap and refrigerate for at least 30 minutes, to allow the mixture to firm up.
When the cheese mixture is ready, add some flour to a bowl or plate. Form the mixture and roll into balls, walnut-sized balls. Then, roll the balls into flour and set aside.
Heat the oil in a pan over medium-high heat until hot and fry 5-6 balls at a time until golden all around.This usually takes about 2-3 minutes.
Remove the cheese balls from the pan with a slotted spoon and place them on a plate lined with paper towels to absorb any excess oil.
Serve warm with tzatziki or tomato sauce. Enjoy!