What is "patty melt"?

A patty melt is a type of sandwich that is made with a hamburger patty, melted cheese, and sautéed onions on grilled bread. The patty melt is typically made with rye bread or sourdough bread, which is buttered and grilled until it is crispy and golden brown. The hamburger patty is seasoned with salt and pepper and cooked on a grill or griddle until it is cooked through. The patty is then topped with melted Swiss cheese and sautéed onions, which are cooked until they are caramelized and tender. The patty, cheese, and onions are placed between the slices of grilled bread, creating a delicious and savory sandwich. The patty melt is a popular food item at diners and cafes, and is often served with a side of french fries or onion rings.