Servings: Serves 4
To make sandwiches: Preheat a grill or grill pan over medium-high heat. Season both sides of the steaks generously with salt, and sprinkle the coarsely crushed peppercorns over both sides of the steaks, patting to adhere. Grill the steaks on both sides until cooked to desired doneness, about 3 to 4 minutes per side for medium-rare doneness.
Remove steaks from the grill and allow to rest for 4 to 5 minutes. Meanwhile, preheat the broiler and heat a large sauté pan over medium-high heat.
Add 2 tablespoons of olive oil to the pan along with the onion and garlic, and sauté for 2 minutes, or until they soften. Add the mushrooms and sauté for 8 minutes, or until tender. Season the mushrooms to taste with salt and pepper, and remove from heat.
Once meat has rested, use a sharp knife and slice into thin slices against the grain. Arrange the baguette pieces on a work surface and layer each bottom piece of the baguette with the sliced steak. Divide the mushrooms among the sandwiches and top with the cheese.
Arrange sandwiches on an oven-safe tray and cook under broiler for 2 to 3 minutes or until the cheese has melted and started to brown.
Remove sandwiches from broiler and allow to cool slightly.
To make topping: In a large mixing bowl, combine the spinach and carrots strips. In a separate mixing bowl, whisk the oil into the vinegar and season to taste with salt and pepper. Toss the spinach and carrots in enough dressing to coat and season with salt and pepper. Arrange the sandwiches on 4 serving plates and serve with the salad and creamed horseradish.