Step 1: Preheat your oven to 375°F (190°C). Prepare your garlic bread by combining the softened butter, minced garlic, and chopped parsley in a small bowl. Spread this mixture evenly over the cut sides of the baguette halves. Place the garlic bread on a baking sheet, butter-side up.
Step 2: Season both sides of the steak generously with salt and freshly ground black pepper. Heat the olive oil or butter in a heavy-bottomed skillet (cast iron works wonderfully) over medium-high heat until shimmering.
Step 3: Carefully place the seasoned steak in the hot skillet. Sear for 3-5 minutes per side for medium-rare, or longer for your desired doneness. For flank steak, aim for a quicker sear to avoid toughness.
Step 4: While the steak is searing, place the garlic bread in the preheated oven. Bake for 8-10 minutes, or until golden brown and fragrant. Keep an eye on it to prevent burning.
Step 5: Once the steak is cooked to your liking, remove it from the skillet and transfer it to a cutting board. Tent it loosely with foil and let it rest for at least 5-10 minutes. This resting period is crucial for juicy steak, allowing the juices to redistribute.
Step 6: After resting, slice the steak thinly against the grain. This makes the steak more tender and easier to eat in the sandwich.
Step 7: Once the garlic bread is out of the oven, immediately sprinkle the shredded cheese over the toasted sides of both baguette halves. You can return it to the oven for 1-2 minutes, or until the cheese is melted and bubbly. Alternatively, use a broiler for about 30 seconds, watching carefully.
Step 8: Arrange the sliced steak evenly over one half of the cheesy garlic bread. If using any optional toppings like caramelized onions or sautéed mushrooms, layer them on top of the steak. Place the other cheesy garlic bread half on top, pressing down gently to form your magnificent sandwich.
Step 9: Cut the assembled Garlic Bread Steak Sandwich into individual portions, usually 2-4 pieces depending on the size of your baguette. Serve immediately and enjoy every glorious bite!