First, gather the bread, cheese, and butter on the counter.
Turn on the stovetop burner on medium-low and let a heavy skillet start to preheat.
Shred the cheese onto a paper plate (for easy clean up or serve the sandwich on it later). This will literally take just 30 seconds.
Spread half of the soft butter on one side of one slice of bread. By this time, the skillet should be hot enough to toast the bread, but not too hot.
Place the slice of bread, buttered side down, in the skillet. Sprinkle the shredded cheese and slice of cheese, if using, on top of the bread.
While the first slice of bread is starting to brown, the cheese will just begin to melt on the underside. This should take 2 or 3 minutes. Meanwhile, butter the other slice of bread with the remaining butter.
Place the second slice of bread. Gently lift a corner of the bottom slice of bread with a spatula. When it is golden brown, slip the flat spatula under the sandwich. Flip the sandwich over. It's ok to use your hand or another spatula to gently hold the top slice of bread down if you are nervous about flipping it.
Cook it 1 minute or until that side is golden brown.