Scrub, pierce, and roll potatoes in warm salted water.
Place on a rack and let skins dry slightly.
Cook at 275°F until around 200°F internally.
Increase to 375°F, oil the potatoes, cook to 205–210°F.
Fry until crisp; reserve 2 tbsp fat.
Cook onion, then cabbage, garlic, and spices.
Stir bacon back in and set aside.
Whisk mayonnaise, chili sauce, relish, mustard, horseradish, onions, parsley, and Worcestershire.
Heat corned beef gently until tender.
Cut open potatoes, melt Swiss inside, add cabbage, beef, more cheese, and dressing.
Plate immediately while hot and steamy.
