For the steak marinade:
- 1/3 cup soy sauce
- 3 tablespoons olive oil
- 3 tablespoons Worcestershire sauce
- 2 tablespoons balsamic vinegar
- 1 tablespoon honey
- 2 smashed garlic cloves
For the sandwich:
- 1 1/2 – 2 pound flank steak
- Fresh cracked black pepper
- Olive oil or vegetable oil
- 1 large onion, peeled and thinly sliced
- 1 tablespoon unsalted butter
- Salt and pepper
- 4 6-inch French or hoagie rolls, sliced in half horizontally
For the jus:
- 2 cups beef stock
- 1/4 teaspoon garlic powder
- 1/4 teaspoon onion powder
- 1/4 teaspoon dried thyme
- 1 tablespoon Worcestershire sauce
For the horseradish mayo:
- 3/4 cup Duke’s mayonnaise
- 2–3 tablespoons prepared horseradish (according to your taste)
- 1 tablespoon finely chopped chives (optional)
- 1 tablespoon Dijon mustard
- 2 teaspoons lemon juice
- Salt and pepper to taste
- This sandwich is a labor of love but wow it’s so worth it. Start by marinating the steak. Combine all of the marinade ingredients in a large zip-to-seal bag and massage to incorporate. Add the steak and allow to marinate for at least 30 minutes at room temperature. You can marinate the steak up to six hours in the refrigerator.
- While the steak marinates, make the jus by combining all of the ingredients in a small saucepan. You’ll heat the jus once the sandwich is assembled but it’s nice to be prepared.
- Make the horseradish mayo real quick by whisking together all of the ingredients in a small bowl. Taste and adjust seasoning to your preference.
- Once the steak has marinated, remove from the bag and pat dry with paper towels. Top generously with fresh cracked black pepper.
- Heat a cast iron skillet over medium-high heat until it’s really quite hot. Add a few glugs of olive oil. Sear steak, about 5 minutes per side, or until you think the steak is a lovely medium-rare. Remove from the pan to a cutting board and tent a piece of foil over the steak to let it rest for at least 15 minutes before slicing.
- Reduce the heat on the skillet to medium-low. Add butter and onions and sauté until tender and just beginning to caramelize, about 6-8 minutes. Season with salt and pepper.
- Once the steak has rested, use a sharp chef’s knife to slice it thinly against the grain at a 45 degree angle.
- Place the prepared jus over low heat to warm.
- To assemble the sandwiches, very lightly toast or rather, warm the sliced rolls on a baking sheet covered in foil under the broiler. This is optional but I like to warm and soften the bread slightly before making this hot sandwich.
- Spread the top side of each roll with horseradish mayo. Place caramelized onions on the bottom of each roll. Top the onions with slices of steak. Season with a sprinkle of salt and pepper. Smash the rolls together. Slice down the center on a slight diagonal and serve with warm jus. Wheeeew it’s good.