For the eyeballs: Place an olive disc in the center of a bocconcini and trace around it with a sharp paring knife. Carve out a 1/2-inch piece of cheese from the outline and place the olive slice in the hole. Wrap a slice of prosciutto around the bocconcini eyeball. Repeat with each bocconcini ball.
For the salsa: Pour the whole can of San Marzano tomatoes into a bowl. Add the olive oil, sugar, salt, balsamic vinegar, Greek oregano, chili flakes, lots of black pepper, the garlic, basil, red onions and parsley. Mix together with your hands.
Divide the eyeballs into pairs and place on individual plates. Add a couple of tablespoons of salsa to each plate. Serve with crostini.