Add 1 tablespoon of butter to the pan and let it melt completely. Place the sandwich in the pan and cook the first side until golden brown, about 1 to 2 minutes. Don’t worry if the cheese hasn’t melted yet—it will finish in the oven. Add the remaining tablespoon of butter, flip the sandwich, and cook the second side until golden brown, another 1 to 2 minutes. Transfer the grilled cheese to a baking sheet.