Miss 20, who is vegetarian, came up with this gastronomic explosion a few months ago when she was hungry for lunch one day. It is pretty easy to make (and actually really nutritious). You do need to use a thick and substantial bread as toast though (we use Vogels, but even a bread like ciabatta rolls would work, as long as it is quite dense).
Buttered, toasted bread (eg Vogels or Burgen)
mustard or mayonnaise
Assemble in the order provided, and grill until the cheese has melted and browned.
I also added some sliced avocado on top of the pickles and under the cheese.