Chris' Best Burgers

Instructions

• Melt butter in a skillet over medium heat and cook and stir onion until nearly translucent, about 4 minutes; remove from heat and cool to room temperature.
• Mix the beef chuck, lamb, onion, Worcestershire sauce, salt, and black pepper in a bowl. Divide the mixture into fifths and form each portion into a large burger. Press an indentation in the center of each burger with your thumb to keep burgers flat while cooking. Chill the patties thoroughly, 4 to 8 hours. Allow burgers to warm to room temperature before cooking.
• Preheat an outdoor grill for high heat, and lightly oil the grate.
• Cook burgers on the hot grill until they show grill marks and the meat is no longer pink inside, about 5 minutes per side. Do not press burgers with a spatula as they cook, and flip only once. Let stand 1 minute before serving.