Preheat the grill to medium-high. For the burgers, put the minced beef, egg, red onion, parsley, thyme and rosemary into a mixing bowl.
Mix well until all the ingredients are combined and herbs are evenly distributed. Divide the mixture into 4 balls and flatten with the palm of your hand to make burger-shapes.
Grill the burgers for 3-4 minutes on each side, until cooked through and piping hot in the middle.
Meanwhile, mix together the mayonnaise, olives and basil for the tapenade. Season with freshly ground black pepper.
Serve the burgers in toasted ciabatta rolls with a spoonful of Italian mayo and garnish with the rocket leaves.