Add the Black Sheep Lamb, mint, harissa, and garlic powder and mix thoroughly, using your hands to combine. Divide Black Sheep Lamb into 6 portions, shaping into 1/4-1/2 in patties.
Cook the burgers over medium heat for 90 seconds on each side or until medium rare. Top with Vertage cheese, cover and cook for another minute or until the cheese melts.
While burgers are grilling, toss arugula with lemon juice and salt and pepper to taste.
Build your burger adding arugula on top of the cheese and patties, in between the burger buns.