Ingredients
2 tbsp. extra-virgin olive oil, divided
8 oz. baby bella or white button mushrooms, thinly sliced
1/4 small yellow onion, very thinly sliced
Kosher salt
Freshly ground black pepper
2 cloves garlic, minced
12 oz. sirloin steak, very thinly sliced
2 tbsp. balsamic vinegar
8 thick slices white sandwich bread
4 tbsp. unsalted butter, room temperature
8 slices provolone cheese
2 tbsp. French’s Creamy Yellow Mustard, plus more for serving
Preparation
Step 1Heat a large skillet over medium-high. Add 1 tablespoon oil. Add mushrooms and onions and season with ¼ teaspoon salt and a few grinds pepper. Cook, stirring often, until onions are sauteed and mushrooms are light golden, about 6 minutes. Add garlic and cook, stirring, until fragrant and golden, about 1 minute more. Remove mushroom mixture from skillet to a heatproof bowl and set aside. Step 2Add remaining tablespoon oil and steak to skillet and cook over high. Season with ¾ teaspoon salt and ¼ teaspoon pepper and cook, tossing a few times until just about cooked through, about 1 minute. Return the mushrooms to the skillet and add the vinegar. Cook, just until vinegar evaporates, about 20 seconds more. Step 3Wipe skillet clean with paper towels and let cool slightly. Step 4Butter one side of each bread slice. Place on a work surface butter-side down. Spread the slices with French’s Creamy Yellow Mustard, then top with half of the cheese, the steak and mushroom mixture, the remaining half of the cheese, and the remaining bread slices.Step 5Heat the large skillet over medium, add two sandwiches. Cook until bread is golden and cheese is melty, 2 to 3 minutes. Flip and cook until golden on other side, 2 to 3 minutes more. Repeat with remaining sandwiches. Serve with more mustard.
