1. Preheat broiler to high.
2. To prepare dressing, combine the first 5 ingredients in a small bowl, stirring well.
3. To prepare sandwiches, place bread slices in a single layer on a heavy baking sheet. Broil bread 1 1/2 minutes or until toasted. Turn bread over; broil for 1 minute or until lightly toasted. Remove 4 slices. Divide cheese evenly among remaining 4 slices, sprinkling it over lightly toasted sides. Broil 1 minute or until cheese melts. Spread about 1 1/2 tablespoons dressing over the cheese-coated side of each bread slice; top each serving with 1 ounce corned beef, 1/4 cup sauerkraut, and remaining bread slices. Serve immediately.