# Step-by-Step:
01 - Arrange the bread slices on a clean surface.
02 - Spread a thin, even layer of mayonnaise on one side of each bread slice.
03 - If desired, apply a thin layer of Dijon mustard on the opposite side of two bread slices.
04 - Place 2 slices of cheese between two bread slices, ensuring the mayonnaise sides face outward. Repeat for the second sandwich.
05 - Preheat a nonstick skillet over medium-low heat.
06 - Place sandwiches mayo-side down in the skillet. Cook for 3 to 4 minutes until the bread is golden brown.
07 - Flip sandwiches and cook for another 3 to 4 minutes, pressing gently with a spatula until the bread is golden and cheese is melted.
08 - Remove sandwiches from skillet, let rest for 1 minute, then slice and serve immediately.