Spread butter on both sides of each piece of bread. On one slice, top with lots of grated cheddar cheese. Put spinach on top of cheese, enough to cover entire slice of bread, but not too think. Put second slice of bread on top.
Fry in skillet over medium heat. Cook each side till brown and crisp and cheese inside is melted. Right before it is done, sprinkle more grated cheese on top of the outside of one side and let it melt. So good! Enjoy!