Open-Faced Steak and Cheese Sandwiches with Malt Vinegar Jus

 

1 ½ pounds flank steak

1/4 cup malt vinegar

2 tablespoons whole-grain mustard

1 tablespoon Dijon mustard

2 tablespoons canola oil

1/2 teaspoon freshly ground black pepper

Kosher salt

1/2 cup beef or chicken broth

1 soft baguette, cut in half and then halved lengthwise (or 4 hoagie buns, split)

12 ounces Gouda cheese, thinly sliced

 

Place the flank steak in a casserole dish. Whisk the vinegar, whole grain mustard, Dijon mustard, 1 tablespoon of the oil, and pepper together in a small bowl, and pour the marinade over the steak. Cover with plastic wrap and marinate in the refrigerator for at least 1 hour, and up to 24 hours. Transfer the steak to a plate, leaving as much marinade as possible in the dish. (Reserve the marinade.) Rub the steak with the remaining tablespoon of the oil, then season with salt on both sides. Preheat the oven to 4OO°F. Line a baking sheet with parchment paper and set aside. Preheat a hot fire (about 5OO°F) in a gas or charcoal grill. When the grill is hot, brush the grilling grates clean. Grill the steak over direct high heat, keeping the lid closed as much as possible, until cooked to your desired doneness, about 5 minutes for medium-rare, turning one time during cooking. Transfer the steak to a cutting board and let rest for 10 minutes. Transfer the marinade to a small saucepan, stir in the broth, and bring to a boil. Reduce heat and simmer for 5 minutes. Arrange the baguette sections cut side up on the prepared baking sheet. Drizzle the baguettes with the sauce. Slice the steak as thinly as possible, divide the slices (and their juices) among the baguette pieces, and top with the cheese. Bake the open-faced sandwiches for about 5 minutes, or until the cheese is bubbling and the bread is toasted.