Heat a skillet over medium heat. Allow it to completely heat before adding any ingredients.

Spread mayo on one side of both pieces of bread. 

Place one slice of bread, mayo side down, into the heated pan. Top with both slices of cheese. If you put them on an angle they will slightly overlap and give you the most cheesy coverage. (Don't forget those drippy bits!)

Top with the other slice of bread, mayo side up.

Cook until the first side is a light golden brown. Flip sandwich to cook the other side to a light golden brown.

Remove from pan and wait a minute or two to slice. Enjoy!