In a large bowl, mix together the lamb, breadcrumbs, egg, lemon zest, rosemary, harissa paste and some salt and pepper. Mix with your hands until well combined.
Shape into four patties and transfer to a plate. Press the centre of each patty to make an indentation, which will help keep its shape during cooking. Cover loosely with cling film and set aside in the fridge.
When the coals are lightly coated with ash and are a medium heat, oil the grill grates and place the burgers on the grill. Cook with the lid on if possible to create an oven and a smokey environment. Grill for 10 minutes, turning once.
Serve the burgers on the toasted buns with some rocket and a dollop of SuperValu Signature Tastes Red Pepper Relish.