In a medium bowl, combine ground beef, egg, Worcestershire sauce, brown mustard, melted butter, bread crumbs, grated Parmesan cheese, minced garlic, and optional onions. Mix gently to maintain texture.

Take about ⅓ pound of the mixture and form into a patty about ¾ inch thick. Indent the center to prevent puffing, then refrigerate for 30 minutes.

Sprinkle your favorite seasoning over both sides of each patty generously for enhanced flavor during grilling.

Preheat the grill to medium-high heat (around 400°F) for perfect searing.

Place patties on the grill and cook for about 4–5 minutes on one side, then flip and grill for another 4 minutes until preferred doneness is reached.

Add cheese on each patty during the last minute of cooking and close the grill lid to melt.

Let the burgers rest for 5 minutes after cooking for optimal juiciness.

Assemble the burgers with the patty, melted cheese, and toppings of choice. Serve immediately.