Avocado Smash: Place the avocado halves in a bowl, fork through to create a rustic mash, add lemon juice, crumbled feta, chopped parsley and tomato. Mix well.
Eggs: Bring a medium shallow fry pan of water and vinegar to the boil then reduce the heat to the water to a simmer. Carefully crack the eggs into a small bowl and then slide into the egg rings in the fry pan.
Allow 3 to 4 minutes for the eggs to firm the whites and have soft runny yolks. Cook longer for a firmer egg. Remove with a slotted spoon, rest on a paper towel to absorb any excess water.
To Serve: Smear the avocado smash on the toasted sourdough and top with 1 egg per slice of bread then season with a pinch of salt on each.