How to Make It
In a large glass baking dish, mix the soy sauce with the sesame oil, sugar, sake, minced garlic, chopped scallions and pepper. Add the skirt steak and turn to coat. Cover with plastic wrap and refrigerate for 2 hours.
Light a grill. Lightly oil the grate. Grill the steak over a medium-hot fire for about 6 minutes for medium-rare meat, turning occasionally.
Transfer the steak to a cutting board and let rest for 10 minutes, then slice across the grain. Serve the steak with lettuce leaves and chili paste and let diners wrap their own beef rolls.