In a bowl, stir together the garlic, mustard, and lime juice. Trim the steak if necessary. Rub steak with mustard mixture and marinate 15 minutes.
Heat a well-seasoned ridged grill pan over moderately high heat until just smoking and grill steak 3 minutes on each side. (Alternatively, broil steak on the rack of a broiler pan about 4 inches from heat.) Transfer steak to a platter and let stand, uncovered, 5 minutes.
With a sharp knife, diagonally cut the steak across the grain into 1/3-inch-thick slices and serve with coleslaw and fries.