Preheat the oven to 400F/200C.
Soak a slice of stale white bread in milk for 10 minutes.
Meanwhile combine ground pork and beef in a large mixing bowl.
Process a medium onion in a food processor with two tablespoons of water until you have a paste or grate it on a grater, add to the mixture.
Add soaked bread together with milk, salt and pepper and mix well with your hands.
Scoop the meat mixture with a 1/3 cup and form an oval shaped patty, flatten it with a palm of you hand. Continue until all mixture is used up.
Heat the oil in a large frying pan and brown patties in batches to avoid overcrowding and steaming.
Fry patties on both sides over medium heat for approximately 5-7 minutes, resist the temptation to flatten your puffed up patties for even cooking.
Put your browned patties in an oven proof pan in a single layer and cook in the preheated oven for additional 10 minutes.