For a great homemade Reuben sandwich, make a quick "sauerkraut" by simmering bagged coleslaw with vinegar and sugar, and replace overly sweet Russian dressing with a simple blend of mayonnaise and Dijon mustard. Oven-grilling allows you to cook the sandwiches all at once (and without turning them) rather than cooking them in batches on the stovetop.
- Adjust oven rack to middle position, place baking sheet on rack, and heat oven to 450 degrees.
- Bring vinegar and sugar to boil in large skillet over medium heat. Stir to dissolve sugar; add coleslaw, cover, and cook, tossing occasionally, until coleslaw is tender, 8 to 10 minutes. Remove lid and simmer until liquid has evaporated, 1 to 2 minutes. Season with salt and pepper.
- Combine mayonnaise and mustard in small bowl.
- Spread 1 tablespoon mayonnaise mixture on each bread slice.
- Layer 1 slice cheese, 1/2 cup coleslaw, 1/4 pound corned beef, and 1 slice cheese on top of bread slice.
- Top with second slice of bread and compress sandwich with your hands.
- Repeat to make three more sandwiches.
- Brush tops and bottoms of sandwiches with melted butter.
- Transfer sandwiches to preheated baking sheet. Bake until toasted, about 10 minutes. Serve.