1 pound ground sirloin
1 pound ground chuck
1 tablespoon Worcestershire sauce
1 teaspoon dry mustard
Coarse black pepper, freshly ground (about ¼ cup)
6 - 2 inch cubes of sharp cheddar cheese
6 hamburger buns
6 crisp lettuce leaves (optional)
6 slices ripe tomato (optional)
Being careful not to over-work the meat, mix the sirloin and chuck, add the Worcestershire sauce, mustard and salt until just combined. Portion the meat into 6 equal pieces and shape each patty around one cube of cheese and set aside.
Meanwhile, put pepper on a shallow plate and roll the rim of each burger in the pepper until it is coated in a "stripe" of pepper. (The burgers can be made up to this point one day earlier and kept refrigerated.)
When ready to grill, place burgers on the cooking grate and grill until the meat is no longer pink, 8 to 10 minutes, turning once halfway through grilling time. Meanwhile grill the buns over Direct heat until lightly toasted, if desired.
Serve immediately on the buttered rolls with a lettuce leaf and tomato if desired. Serve with traditional condiments on the side.