- Place each chicken piece between 2 sheets of plastic wrap. Using a meat tenderizer, gently pound to a uniform thickness of 1/4 inch. Place in a glass bowl and rub evenly with the lemon juice.
- In a small, dry fry pan over low heat, toast the sesame seeds, stirring occasionally, until fragrant and golden brown, 3 to 5 minutes.
- Set aside 1 tablespoon of the toasted seeds. Transfer the remaining 1 tablespoon seeds to a mortar and grind with a pestle, or transfer to a spice grinder and grind to a powder.
- In a small bowl, stir together the ground sesame seeds, garlic, minced green onions, soy sauces, sugar, sesame oil, ginger and pepper. Pour over the chicken, turn the pieces to coat evenly, cover and refrigerate for at least 3 hours or as long as overnight.
- Prepare a fire in a grill.
- When the coals are hot, place the chicken pieces directly on the grill rack. Grill until lightly charred, about 5 minutes. Using tongs, turn and cook until charred on the other side, 3 to 4 minutes more. Alternately, preheat a stovetop grill pan over medium-high heat. When hot, spray the cooking surface lightly with oil or nonstick cooking spray. Grill the chicken until lightly charred, about 4 minutes per side.
- Transfer to a serving platter. Sprinkle with the reserved sesame seeds and the slivered green onions and serve.