Divide the corned beef evenly among the 4 open-faced slices (about 3 oz per sandwich). Pile the drained sauerkraut evenly over the corned beef (about 1/4 cup per sandwich). Top each with 2 slices of Swiss cheese.

Place the remaining 4 slices of rye on top, butter-side-up, to form 4 sandwiches.

Heat a large skillet or griddle over medium-low to medium heat. Place the sandwiches in the pan and cook 3–4 minutes per side, pressing gently with a spatula or a sandwich press, until the bread is golden brown and the cheese is melted. If the bread is browning too quickly before the cheese melts, lower the heat and cover the pan for 1–2 minutes to help the cheese soften.

Remove sandwiches from the pan and let rest 1 minute, then slice each sandwich in half on the diagonal and serve immediately.

For the Russian/Thousand Island-style dressing

In a small bowl, combine mayonnaise, ketchup, prepared horseradish, sweet pickle relish, Worcestershire sauce, hot sauce (if using), and lemon juice.

Season with salt and freshly ground black pepper. Taste and adjust — add more horseradish for heat, more relish for sweetness, or more lemon for brightness.

Cover and refrigerate for at least 15 minutes to let the flavors meld. This makes about 6 tbsp of dressing—enough to spread on 4 sandwiches.