Heat the olive oil over a medium heat in a frying pan or skillet and cook the onion for 5 minutes until softened. Add the garlic and salt and pepper to taste and cook for another couple of minutes. Pour in the passata and add the oregano and turn the heat up slightly.
Cook for 10-15 minutes until reduced enough that you can make 4 wells in the sauce without it running back into the gaps. Crack an egg into each well and cover the frying pan, cook for 5-7 minutes, until the whites have set and the yolks are still runny. Serve sprinkled with grated parmesan, basil leaves and crusty bread.