1.  Put beef in a zip top plastic bat set in a shallow dish.  Stir together soy sauce, green onion, sugar, garlic, sesame seeds, sesame oil and pepper in a small bowl.  Whisk to blend, pour over beef.  Seal bag and turn to coat.  Chill at least 1 hour or up to overnight. 

2.  Preheat a grill pan (or any large pan for stir frying) over medium high heat, lightly oil pan. 

3.  Remove beef from bag, discarding marinade.  Grill until slightly charred and cooked through, 1-2 minutes per side.  Serve beef mixture in lettuce leaves with Kongamul.  Garnish with additional green onions. 

Kongamul:

Bring a pot of lightly salted water to a boil.  Add 8 oz soybean or mung bean sprouts: cook, uncovered, until tender, yet crisp, about 15 seconds.  Drain and immediately immerse in ice water several minutes, then drain again.  Whisk together 2 T. sesame oil, 1 T. each soy sauce and gochugaru (Korean red chili pepper flakes), 1 t. each sesame seeds and rice wine vinegar and 1/4 tsp minced garlic in a bowl.  Stir in sprouts, toss to coat.  Top with 2 T. sliced green onion.  Chill at least 1 hour or up to 3 days before serving.