01 - Preheat the air fryer to 375°F for 3 minutes to ensure even toasting.
02 - Spread softened butter evenly onto one side of each bread slice using a butter knife.
03 - Arrange two slices of bread, buttered side down, on a clean work surface. Layer each with two slices of cheese, and include any optional add-ins if desired.
04 - Place remaining bread slices on top, buttered side up, to complete the sandwiches.
05 - Arrange the sandwiches in the air fryer basket in a single layer, ensuring they do not overlap; cook in batches if necessary.
06 - Air fry the sandwiches for 4 minutes, allowing the bread to begin crisping.
07 - Carefully flip the sandwiches with a spatula and air fry for an additional 3 to 4 minutes until deep golden brown and cheese is fully melted.
08 - Remove sandwiches from the air fryer, let rest for 1 to 2 minutes, then slice and serve hot.