Choose the right cheese and bread for reliable results. Cheddar, Gruyère, American, or fontina are excellent melters. Use a sturdy but not overly thick bread like sourdough, pullman loaf, or country white. Butter the outside of each slice evenly for deep browning.
Cook slowly on moderate-low heat. Place the sandwich in a preheated skillet over medium-low heat. Cook covered for a few minutes to trap heat and encourage even melting, flipping once when the first side is golden brown. Cooking too hot will brown the bread before the cheese melts.
Key steps and options:
Variations include adding caramelized onions, tomato slices, ham, or apple slices for sweet contrast. For extra crispness, finish in a 375°F oven for 3–5 minutes after pan-searing. The goal is a balance of deeply browned exterior and uniformly melted cheese inside.