Heat a non-stick pan over medium heat until hot (about 3 minutes) then reduce heat or low.
Add cheese to one slice of bread
Sandwich with the remaining bread
Butter both sides of the bread generously
Cook in the pan over low heat until the cheese is melted and both sides of the sandwich are golden brown. This can take longer with non-dairy cheese, so I recommend cooking each side for 4 minutes. You can then turn up the heat to medium and brown the bread.