Cut a ¼ of the onion into thin slices and then finely chop the rest. Mix the pork with the breadcrumbs, chopped onion, oregano, egg, half the garlic and some seasoning. Mix well and form into 12 small patties. Mix the remaining garlic with the radishes and yogurt in a small bowl. Chill until needed.
Rub the patties with a tiny bit of oil and chargrill in a pan or on the barbecue for 4-5 minutes a side until cooked through. Mix the sliced onions and tomatoes and serve with the patties, tzatziki and some warm pitta breads.