Peel and cube potatoes. Boil for about 20 minutes until tender. Drain and set aside.

Preheat oven to 350 degrees. Drain the sauerkraut. Do NOT Rinse. Chop the onions and add to the sauerkraut in an oven proof casserole. Bake uncovered about 30 minutes.

Prepare a baking sheet with parchment paper. Center a sheet of phyllo pastry on it and spray with cooking spray. Add another sheet and spray again. Continue until you have 5 sheets sprayed.

Cover the pastry sheets with the meat slices leaving about 2" from the outer edges of the pastry. Drizzle with mustard or Thousand Island Dressing if using.

Combine the potatoes, sauerkraut mixture and 1 ½ tsps caraway seeds in a bowl. Spread this mixture along the center of the pastry. Mound it quite high so the edges of the pastry and meat are still clear.

Top the mound with the Swiss Cheese.

Fold the short ends of the pasty toward the center. You will have a couple of inches of pastry tucked toward the center. Then carefully fold/roll the long edge toward the other long edge. Turn the roll gently so the final edge is now on the bottom of the roll. This will help keep the roll secured.

Brush the outside with melted butter and sprinkle with caraway seeds.

Baked at 350 degrees for about 45 minutes. Pastry will be golden brown.

Slice and serve with dill pickles and dollops of sour cream. Drizzle more mustard or dressing to taste if desired.