Preheat grill to medium, medium-high heat. Combine all ingredients in a bowl. With cold-water dampened hands, shape into 4, 3/4-inch thick patties. Grill, lightly oiling the surface first, 4-5 minutes per side, or until entirely cooked through. Serve as is with chutney, or sandwich in naan bread, pita or a burger bun garnishing, if desired, with tomato, onion, lettuce and yogurt.