Prepare Mac and Cheese. (If using frozen mac and cheese, prepare according to package instructions). This recipe works great with leftover mac and cheese. If using leftover mac and cheese, heat in the microwave for 1-2 minutes, or until warm.
Butter one side of each slice of bread. On two of the slices, buttered side down, add one slice of cheese and a portion of the prepared mac and cheese. Top each with another slice of cheese and the two remaining slices of bread, buttered side up.
Grill each sandwich on a skillet or griddle over medium heat until bread is golden brown and toasted, about 3-4 minutes. If bread is toasted but cheese is not fully melted, lower heat and cover pan for another 1-2 minutes, or until cheese is melted.
Serve and enjoy!