1. Preheat oven to 350.
  2. Toss bread with butter, place cubes on baking pan and lightly toast in oven for 5-7 minutes.
  3. Meanwhile, whisk together eggs, milk, dressing and mustard. Season with salt and pepper.
  4. In a large bowl, combine toasted bread with corned beef, sauerkraut, 2/3 cup cheese and all green onions except 1 tablespoon. Pour egg mixture over bread cube mixture and gently stir to combine. Place combined egg and bread mixture in 11 x 7 baking dish.
  5. Bake uncovered for 35-40 minutes or until liquid is nearly absorbed. Top with remaining cheese and bake another 5 minutes or until cheese is melted. Sprinkle with remaining green onions and allow to cool for 5-10 minutes before serving.