Chop the herbs and pepper and mix with the meat and the egg in a large bowl. Divide into 4 balls and flatten with the palm of your hand.
Grill the burgers for 3-4 minutes on each side.
Serve the burgers in toasted Ciabatta rolls with a spoonful of the caramelised onion mayonnaise and garnish with rocket leaves.
Recipe courtesy of Hellmann's