4 large russet or Idaho potatoes, scrubbed clean
2 tablespoons spicy brown mustard
1/4 cup milk, plus additional (depends on how thick you like them)
2 tablespoons butter
Salt and ground black pepper
1/4 cup chives, chopped
2 cups leftover corned beef or thick deli slices (each about 1/4 inch), chopped
1 cup leftover cooked cabbage, shredded or sauerkraut
1 tablespoon malt or cider vinegar (if using leftover cabbage, omit if using sauerkraut)
1 cup Swiss cheese, shredded
1/2 cup sour cream
2 tablespoons pickle relish
1/4 cup ketchup
Pre-heat oven to 400ºF.
On a baking sheet, roast the potatoes until cooked through, about 45 minutes. When cool enough to handle, cut a quarter of an inch slice off the top of the potato to create a large boat. Scoop out all the potato flesh into a medium bowl, keeping the skin intact.
Mash the potato flesh with the spicy brown mustard, milk, butter, salt, ground black pepper and chives. Fold in the chopped corned beef. Fill the potatoes with the corned beef-potato mixture so they are over-stuffed. Combine the cabbage with the vinegar (or you can use sauerkraut). Pile cabbage or sauerkraut over the potatoes then top with shredded Swiss cheese. Pop into the oven until golden and bubbly on top.
While the potatoes are in the oven, combine the sour cream, pickle relish and ketchup. Serve a potato per person, garnished with a dollop of the Russian-style sour cream.