Beef on Weck Sandwiches

Preheat the oven to 400°F. Wash and dry the fresh produce. Heat a small pot of salted water to boiling on high. Cut the potatoes into ½-inch-thick rounds. Peel and thinly slice the onion. Slice the rolls in half horizontally. In a small bowl, combine the mayonnaise and horseradish; season with salt and pepper to taste.

Once the pot of water is boiling, add the potatoes. Cook 12 to 14 minutes, or until tender when pierced with a fork. Drain thoroughly and transfer to a large bowl. Add the mustard, one-third of the arugula and all but a splash of the vinegar. Toss to coat and season with salt and pepper to taste. Set aside. Rinse and wipe out the pot.

While the potatoes cook, in a medium pan (nonstick, if you have one), heat 2 teaspoons of olive oil on medium-high until hot. Add the onion and cook, stirring frequently, 10 to 12 minutes, or until completely softened and thoroughly browned. (If the onion starts to burn, add 1 tablespoon of water and reduce the heat to medium.)

Using your hands, separate the layers of the shaved beef. Add the beef to the pan of caramelized onions with ¼ cup of water. Cook, stirring frequently, 3 to 5 minutes, or until the beef is just cooked through. Remove from heat; season with salt and pepper to taste.

While the beef cooks, in the same pot used to cook the potatoes, combine the beef demi-glace, remaining vinegar and ¼ cup of water. Cook on high, stirring occasionally, 2 to 3 minutes, or until the mixture comes to a boil. Once boiling, remove from heat. Season with salt and pepper to taste and set aside.

Place the rolls, cut side up, on a sheet pan. Toast in the oven 4 to 6 minutes, or until lightly browned and crispy. Transfer the toasted rolls to a clean, dry work surface. Top with the cooked beef and caramelized onions, horseradish mayonnaise and remaining arugula. Divide the sandwiches and potato salad between 2 plates. Serve with the jus on the side for dipping. Enjoy!