Heat a skillet over medium heat. Butter one side of each slice of rye bread. Apply 1 tsp whole grain mustard on one slice of the bread. Place one slice in the skillet, butter-side down, and top with Swiss cheese. Add the second slice, butter side up.
Cook 2–3 minutes per side, pressing gently with a spatula, until the bread is golden and the cheese is fully melted.
Transfer to a cutting board and let cool for about 1–2 minutes so the cheese firms up slightly. Cut the sandwich into ¾-inch cubes to make grilled cheese croutons. Set aside.
In the same skillet, melt 1 tablespoon butter over medium-high heat. Add the drained 1 cup sauerkraut and spread it into an even layer.
Let it cook undisturbed for about 3–4 minutes so the bottom forms golden, caramelized edges.
Toss and cook for another 1–2 minutes until lightly browned and fragrant. Transfer to a small bowl and set aside.
Return the skillet to medium-high heat.
Add the sliced 12 oz corned beef in a single layer. Sear for 1–2 minutes per side until lightly caramelized and heated through. Work in batches.
Transfer the beef to a plate, leaving the flavorful drippings in the pan.
Reduce the heat to medium-low. In the same skillet, add: 2 tablespoons Country Wholegrain Mustard1 tablespoon Caramelized Onion & Garlic Jam and 2 teaspoons Bourbon Molasses Sauce, 1 tablespoon apple cider vinegar, 3 tablespoons beef broth and ½ teaspoon caraway seeds.
Whisk everything together and cook for about 2 minutes, until the jam melts and the dressing becomes glossy and pourable.
Taste and adjust with a little more vinegar, salt, or pepper if needed. Keep warm on very low heat.
In a large bowl, gently toss together: 4 ounces arugula and 1 cup green cabbage. Spread the greens across a large serving platter or divide between plates.
Layer the warm seared corned beef over the greens.
Scatter the caramelized sauerkraut throughout the salad. Add the grilled cheese croutons.
Spoon the warm mustard dressing generously over the top.
Finish with sliced 2 tablespoons green onion, 2 tablespoons fresh dill and a few cracks of black pepper.
Serve immediately while the beef is warm, and the croutons are still crisp.
Notes
Dry the sauerkraut well- sauerkraut holds a lot of liquid. After draining, gently press it with paper towels.Don’t overcrowd the corned beef - give the slices space in the skillet so they sear properly. Let the grilled cheese rest before cutting - give the sandwich a minute or two after cooking so the melted cheese sets slightly.