Adapted from here.
To make the dressing, add soy sauce, vinegar, 1 tablespoon vegetable oil, sesame oil and ginger to a mason jar. Cap and shake until well combined. Set aside.
Prepare a charcoal grill to medium-high heat using Kingsford® Original Charcoal Briquets. Let the grill grate preheat for 15 minutes, and clean and oil it just before cooking. Brush mushrooms and steak with oil, then season mushrooms with salt and season both sides of the steak liberally with salt and pepper.
Grill mushrooms, turning often, until tender, golden and charred in spots (4 to 6 minutes). Sear steak until golden and charred in spots (about 4 minutes), then flip the steak and continue to cook until the internal temperature reaches 120°F for rare, 130°F for medium-rare, and 140°F for medium ( 2 - 3 minutes more). Transfer mushrooms and steak to a plate, and let steak rest for 5 minutes before slicing.
Tear mushrooms into bite-sized pieces and slice steak against the grain. Add mushrooms, arugula and scallions to a large bowl, and toss with some of the dressing. You want the vegetables evenly coated, but not swimming in it. Divide steak and dressed salad between 2 to 4 plates, then top with toasted sesame seeds, sliced chiles, mint leaves and a sprinkling of flaky sea salt.