Heat oven to 375°F. Unroll 1 can of dough onto large ungreased cookie sheet. Spread Thousand Island dressing on dough to within 1/2 inch of edges. Top with corned beef, Swiss cheese and sauerkraut.
Unroll remaining can of dough on work surface. Spread mustard to within 1/2 inch of edges. Place mustard side down on sauerkraut. Press edges with fork to seal. Brush with egg. Sprinkle with sesame seed.
Bake 20 to 25 minutes or until deep golden brown. Cut into slices to serve.