Before you start: Prepare dressing and assemble: 15 minutes Warm beef and toast sandwiches: 15 minutes Use the listed ingredient state: dry, cooked, thawed, drained or squeezed. Times are estimates; follow the doneness cues. This recipe starts with fully cooked corned beef.
Recipe note: Refrigerate perishable leftovers promptly in shallow containers; use within 3–4 days and reheat to 165°F. Count storage from the original cooking date when using leftovers. Refrigerate perishable cooked dishes in shallow containers within 2 hours, or 1 hour above 90°F; keep the refrigerator at 40°F or below.
Keep the filling from wetting the rye
Drain and squeeze the sauerkraut before building the sandwiches. The dressing already supplies moisture, so wet cabbage can soften the bread before the cheese melts. Divide the filling into three piles beside the bread rather than filling the first sandwich generously and leaving the last one short. Keep the buttered surfaces on the outside.
Have a plate ready before the skillet heats. Once the first side is crisp, turn with a wide spatula that supports the sandwich instead of gripping its middle with tongs.
Give the cheese time to melt
Medium-low heat lets the filling warm while the bread colors. If the rye is getting dark before the cheese softens, reduce the heat rather than pressing harder. Pressing can squeeze dressing into the pan and make turning messier. Cook in separate rounds when the sandwiches would touch or prevent the spatula from sliding underneath.
Keep the small pause between batches brief and serve from the first finished round if needed. A crisp sandwich is most enjoyable soon after cooking; making all three fit a cramped skillet is not worth losing control of their surfaces.
Timing and servings are estimates. Equipment, ingredients and portion sizes affect the result.