In a large bowl, combine the garlic, lemongrass, fish sauce, soy sauce, pepper and sugar. Add the chicken and toss to coat. Cover and refrigerate for 30 to 60 minutes.
Preheat the grill to medium heat. Brush the grill grates with oil. Cook the chicken over direct heat for five to seven minutes per side or until it reaches an internal temperature of 165°F. Editor's Tip: Use a meat thermometer to check the chicken's doneness.
In a small bowl, combine the lime juice, fish sauce, sugar and chili garlic sauce. To serve, garnish the chicken with the nước chấm and green onions. Editor's Tip: Make extra nước chấm. It tastes great on grilled meats, spring rolls and noodle dishes, just to name a few items. Also, you can use it as a dipping sauce or mix it into a salad dressing.
