Directions

1. Preheat grill to medium (300°F to 350°F). In a large bowl combine beef and 2 tablespoons of the mustard. Form into 4 patties. Lightly coat patties with peppercorns, pressing to adhere.
2. Place patties on grill. Grill 4 minutes per side (160°F for medium) or to desired doneness. During the last 2 minutes of grilling, top each patty with 1 cheese slice; grill until melted.
3. Meanwhile, for the sauce, in a small bowl combine remaining 1 tablespoon mustard plus mayonnaise, onion and vinegar. Set aside.
4. Place rolls cut side down on grill. Grill until lightly toasted. Spread sauce on cut sides of rolls. Place burgers in rolls, top with arugula and tomato, and serve.