Spread 1/4th of the butter or mayo on one side of each piece of bread.
Place one slice of bread with the butter side down into the basket of the air fryer. Add 3 pieces of cheese on top of the slice of bread. Place another piece of bread on top of the sandwich, butter side up.
Close the air fryer and cook for 4-5 minutes until lightly golden brown, flip the sandwich over and cook an additional 2-3 minutes or until the toastiness of your liking.
Repeat with the remaining ingredients.
Serve with your favorite sides.
Notes
Don't overcrowd the basket.
Not all air fryers cook the same. Check about halfway through cooking and adjust the time, if needed.
This is just a basic recipe, experiment with your favorite cheese and mixins such as deli ham, sliced tomatoes, etc.