Full Guide [natashaskitchen.com]
1 Spread half a tablespoon of butter on one side of each two slices of bread.
2 Place a skillet over low to low-medium heat. If you’re using a griddle, it should be at 135˚C. Immediately add both slices of bread with the buttered side down.
3 Stack the cheese on one of the pieces of bread, then cover it with the other piece of bread and flip the sandwich over.
4 Continue sauteing - flipping once - until both sides are gilded brown and the cheese has melted.
5 Cut the sandwich in half on the diagonal to serve.