Break the stock ends off the 4 romaine leaves to make them equal in size. Place them on a plate at the 4 corner positions. Rip the stock ends into small pieces and sprinkle them on top of the corner leaves. Place a tomato slice on top of them. Place two cucumber slices beside each other on top of the tomato slices. Sprinkle equal amounts of the chopped green onion and parsley over the cucumber slices. Sprinkle salt and pepper to taste over all.
Whisk together the balsamic vinegar and olive oil until well combined; drizzle over each corner salad.
Pass and serve with a pie slicer that can be placed under each individual corner salad to pick each up and place on individual salad plates.