01 -
Evenly spread softened butter on one side of each bread slice. If desired, spread Dijon mustard on the opposite side of two slices.
02 -
On the unbuttered side of two bread slices, layer ham followed by Gruyère cheese. Top with remaining bread slices, ensuring the buttered side faces outward.
03 -
Preheat a skillet or sandwich press over medium heat. Place the sandwiches buttered side down and cook for 4 to 5 minutes per side, or air fry at 350°F for 7 to 10 minutes until golden brown and cheese is melted.
04 -
In a small bowl, combine milk with grated Gruyère. Add salt and black pepper to taste, mixing until smooth.
05 -
Spoon the cheese mixture over the top of each sandwich in the final minutes of cooking. Optionally, transfer sandwiches to a broiler for 2 minutes until cheese is melted and lightly golden.
06 -
Serve hot, immediately after broiling, for optimal crispness and melt.