Make the pickled apples a few days ahead or the morning you would like to make the tartine.

Preheat the oven to 450°. Spread butter evenly on one side of 4 slices of bread, place the bread on a foil lined baking sheet sprayed with cooking spray, butter side down.

Spread mustard over the four slices of bread.

Sprinkle the mustard side with a little shredded cheese, then add 2 slices of ham, then 3 slices of pickled apple and 2 slices of gruyere cheese to each slice of bread. Then sprinkle a little more of the grated Swiss cheese over the top of the tartine.

Bake until cheese is melted and golden around edges, 6-8 minutes. Add a sprinkle of cracked pepper and enjoy.