HERB BUTTER-STUFFED BURGERS

Steps:

• Make the herb butter: Mix the butter, parsley, garlic, lemon juice, Worcestershire sauce, 1/2 teaspoon salt and a few grinds of pepper in a small bowl. Transfer to a piece of plastic wrap and form into a 4-inch log. Wrap and freeze until firm enough to slice, about 20 minutes. Slice the butter log into 8 rounds.
• Make the burgers: Preheat a grill to medium high. Divide the ground beef into 4 mounds, place a slice of butter on each, then gently shape the beef around the butter to enclose. Press the beef into four 4-inch-wide patties (about 1/2 inch thick). Refrigerate until ready to grill. Set aside the remaining butter for serving.
• Season the burgers on both sides with salt and pepper. Grill until well marked, 3 minutes. Flip and top each with a slice of cheese. Cook 3 more minutes for medium rare, covering during the last 15 seconds to melt the cheese. Grill the buns until toasted.
• Spread the remaining herb butter on the bottom buns. Serve the burgers on the buns with mustard, onion, tomatoes and lettuce. Skewer cornichons on toothpicks and insert into each burger.