Spread butter on just one side of both slices of bread.
Heat a griddle or griddle pan to medium-low heat. (You don't need to spray with cooking spray).
Place both slices of bread, with the buttered sides facing down, on to the griddle. Place both slices of cheese stacked on top of each other on one of the bread slices. Cook for 2-3 minutes.
Using a spatula, carefully, lift each slice up to check the golden coloring of the bread. Once both slices are looking golden brown, use the spatula to stack the solo slice onto the slice with cheese. Press on the sandwich with your spatula, and flip over a few times until the outsides are fully golden brown and the cheese is melted.
Carefully remove from griddle with spatula and enjoy!