Divide some mustard on 2 slices of bread. Then add a layer of cheese, some pickles and more cheese. Top it off with the other slice of bread.
Melt 1 tablespoon of butter in the baking pan. Add the sandwiches and bake them brown and crispy. When you turn the sandwiches on the other side, you can add the other tablespoon of butter. Make sure the pan is not too hot, since the cheese needs some time to melt as well.