Meanwhile, prepare the filling. Preheat a large frying over medium-high heat, add a splash of oil and fry the ground beef for 7 to 8 minutes, breaking it up into small pieces. Let the meat cool until just warm. Place the onion and garlic into a
food processor and pulse into a puree. Alternatively, use a grater to puree the onion and finely mince the garlic. In a
large bowl combine all of the filling ingredients: fried beef, pureed onion, garlic, cheeses, egg and seasonings. Use your hands to knead the ingredients together to form a uniform mixture.