This is so simple yet so tasty. I recommend using white sourdough bread for these sandwiches. The whole wheat sourdough is so strong you can't taste the ham and cheese. This recipe is for two sandwiches, so be sure to double as needed. Use your favorite mustard...dijon, german, grain, etc.
4 thick slices sourdough bread
4 slices ham
2 thick slices cheese, any flavor
equal parts mayonnaise and mustard (about 1 tbsp each per sandwich)
olive or canola oil
Mix together mayonnaise and mustard. Spread on one side of all four slices of bread. Place 2 slices of ham and 1 slice of cheese between two slices of bread with the mayo mixture touching the ham; repeat for 2nd sandwich.
Brush outside of sandwich with oil. On a skillet (preferrably cast iron), grill sandwiches on medium low heat until cheese is melted and outside bread is golden brown.