Kraut -- Lets get the sauerkraut layer started. Add 1 teaspoon of the butter to a small saute pan and melt on medium high. Add the onions and caraway and cook until soft and slightly golden brown, Maybe 4-5 minutes. Add the sauerkraut (drained) and let simmer on medium low until every thing is combined and some of the liquid reduces.
Fish -- First the fish should be taken out of the fridge so they are close to room temperature Then in a pie pan or small dish add the flour, cayenne, salt and pepper. Dip the fish in the flour mixture and coat both sides, just to get a light coating. This is not a heavy crust, just a light crust is all.
Saute -- In a large saute pan, add 1 tablespoon of the butter and bring to medium high heat. Saute the fish until golden brown on each side. They will only take 2-3 minutes per side. Remove and let cool for just a minute or two.
Use a fork and lightly break up the fish, not flaked like canned tuna, just break it up lightly so it isn't "one whole piece" on the sandwich.
Sandwich -- Now build the sandwich, 1 slice of bread topped with thousand island dressing (go easy on the dressing), cheese, fish, then top with a couple of spoons of the sauerkraut and onions. Next, a slice of cheese and bread with thousand island spread on the inside, then repeat. Topped with more thousand island (again go easy), cheese, fish, sauerkraut, cheese and the final bread for the top.
Remember this is a double decker sandwich so don't make the layers too thick.
Grill -- In a saute pan or grill pan. Spread the outside top and bottom with a light "smear" of butter and grill on medium to medium low to toast the outside and get nice and golden brown. As they grill I like to cover so the cheese melts. Use a large lid or just a piece of foil will work fine, just don't grill on high, let it go slowly. Cut these in half and serve 1/2 per person they are big and delish!