Freeze steaks until firm, about 30 minutes.
Warm a nonstick pan over medium heat. Place sesame seeds in the dry pan. Stir or flip occasionally, until toasted. Watch carefully, they burn quickly. Remove from pan to cool. Crush in a blender, food processor, or with a mortar and pestle-- I'm not choosy.
Remove steak from freezer when firm (not frozen). Cut steak against the grain into 1/4-inch slices.
In a large resealable bag, combine soy sauce, sugar, chili garlic sauce, and sesame seeds. Place strips into marinade, making sure to incorporate all meat in mixture. Place in refrigerator for 4 hours.
Once ready to eat, heat the grill so that it is hot, hot, hot. Thread beef onto metal or soaked wooden skewers; discard any remaining marinade. Grill beef, covered, for 2-3 minutes on each side, until the desired doneness.
If desired, sprinkle with thinly sliced green onions & chopped cilantro.