Mushroom Steak Melt

Ingredients

• 2 tablespoons olive oil
• 4 portobello mushrooms, stems removed and sliced
• Salt and pepper to taste
• 1/2 cup diced onion
• 1/4 teaspoon garlic powder
• 2 tablespoons Worcestershire sauce
• 4 slices of provolone cheese
• 4 hamburger buns

Directions

1. Set an oven rack about 6 inches beneath the broiler, then turn the broiler to high. Stir the beer, mustard, Worcestershire, and vinegar together in a small bowl, and keep it nearby. Place your cast-iron skillet, 10- to 11-inch, over medium-high and let it warm for about 2 minutes. While the pan heats, cut the flap meat as needed so it fits in the skillet, then season it well with salt and pepper. Switch on the exhaust fan. Add the oil to the hot pan and rotate it to coat the surface. Lay in the meat and cook, flipping about every 2 minutes, until it reaches 135°F, 5 to 10 minutes total. Move the steak to a cutting board, cover it loosely with foil, and set it aside.
2. Turn the heat down to medium, then add the mushrooms, onion, and rosemary to the skillet. Sprinkle with salt and pepper, and cook, stirring often, until the mushrooms have given off their liquid and begin to catch on the pan, 6 to 8 minutes. Spoon the mixture into a bowl.
3. Set the skillet back over medium heat. Pour in the beer mixture and cook, using a wooden spatula to scrape up the bottom of the pan, until the liquid cooks down into a light glaze, 5 to 7 minutes. Take the skillet off the heat and stir in the mushrooms and onion. Slice the meat thinly across the grain, then toss it with the mushroom mixture.
4. Place the bread directly on the rack beneath the broiler and toast it on both sides, about 1 minute per side. Move the toasted bread to a small baking sheet. Divide the steak mixture among the slices, then top with the cheese. Broil until the cheese is melted, 1 to 2 minutes. Serve.