Classic Cheeseburger

Ingredients

• 1 pound ground chuck (80% lean)
• 1 pound ground sirloin
• Pendery's Sea Salt
• Pendery's freshly Cracked Black Pepper
• 4 to 8 burger buns
• 1/3 cup yellow mustard
• 1 tablespoon butter
• 8 slices American cheese
• 4 to 8 (1/4-inch-thick) tomato slices
• 4 to 8 (1/4-inch-thick) red onion slices
• Pickle slices
• 8 burger-size lettuce leaves
• Ketchup, for serving
• Mustard, for serving