Here are the following ingredients:
Here are the following shopping items to buy:
Follow these cooking methods/directions:
Heat oil in heavy skillet over medium heat; cook mushrooms, garlic and onion, stirring occasionally, for about 8 minutes or until onion softens and mushrooms are lightly caramelized and liquid has evaporated. Stir in balsamic vinegar; cook, stirring for 3 to 5 minutes or until vinegar is absorbed. Season with salt and pepper to taste; set aside.
Rub steaks with salt and pepper to taste. Lightly oil cast-iron skillet or grill and cook over medium-high heat (in a closed barbecue) for 6 to 8 minutes for ¾ inch (2 cm) thick steaks, turning twice or more, for medium-rare 145°F (63°C) at the least.
Transfer to cutting board and let rest for 5 minutes. Cut steaks in half crosswise
Brush insides of rolls with mustard, spoon mushroom mixture into rolls and add steaks. Top with chèvre and arugula.