Toast the coriander in a pan for 1 minute. Coarsely grind in a coffee grinder. Dice onion, mince garlic. Mix all ingredients except 4 teaspoons of coriander together. Form into burgers. Coat each burger with 1 teaspoon coriander. Grill thoroughly and serve (on rolls with ketchup, tomato, fried onions, Feta cheese, etc.).