1Grate the red onion or blitz it and add to a bowl. Finely chop the fresh parsley and mint and add to the same bowl.
2Add the egg, breadcrumbs, beef mince and seasoning to the bowl and mix until well combined.
3Take about a tablespoon of the mixture, flatten it, place a cube of the Kefalotyri in the middle, and roll the mince into a ball to cover. Smooth the edges using the palm of your hand to form a flat burger shape. Repeat with the remaining mixture.
4Over high heat, add the oil to a frying pan and heat for 2 minutes or until a wooden spoon fizzes when poked into the oil.
5Place the burgers in the pan and cook for 3-4 minutes on each side until crispy and golden.
6Remove the burgers and place on a plate lined with kitchen roll to drain the excess oil.