# Method:
01 - Place the bread slices on a clean surface to prepare for spreading.
02 - Spread a thin, even layer of mayonnaise on one side of each bread slice.
03 - If desired, spread a thin layer of Dijon mustard on the opposite side of two bread slices.
04 - Place two slices of cheese between two bread slices with mayonnaise sides facing outward; repeat for the second sandwich.
05 - Heat a nonstick skillet over medium-low heat until warm.
06 - Place sandwiches in skillet, mayonnaise side down, and cook for 3 to 4 minutes until golden brown.
07 - Flip sandwiches and cook for another 3 to 4 minutes, pressing gently with a spatula, until bread is golden and cheese melts.
08 - Remove sandwiches from skillet, let rest for 1 minute, then slice and serve immediately.