Easy-peasy. Grated onion (not so easy on the eyes), mix it up with lamb mince and garlic, then add herbs and spices if you like - thyme is good. Shape them into patties and grill away!
One thing I like to add as a relish is a basic Italian tomato sauce (slice garlic, fry for 1 minute, add canned tomatoes and simmer for 45 mins). I just add a bit of chilli, reduce it until it's thick and pop it on top of each burger. Yumyumyumyum!