Prepare the lemongrass, garlic & ginger. Trim away the dry top and root end. Remove the tough outer layers and finely mince the tender pale section. Finely chop garlic and grate the ginger.
Make the marinade. Combine the lemongrass, garlic, shallot, fish sauce, soy sauce, sugar, oil and black pepper into the chicken
Marinate the chicken. Add the chicken thighs and coat thoroughly. Cover and refrigerate for at least 2 hours, preferably 4 to 6 hours or overnight.
Preheat the BBQ. Heat your grill to medium-high to high heat.
Grill the chicken. Shake off any large pieces of marinade and cook the chicken for approximately 4 to 6 minutes per side.
Check for doneness. Cook until the chicken reaches an internal temperature of 75°C and has plenty of caramelised colour around the outside.
Slice and serve. Slice across the grain and pour any resting juices over the chicken.Serve with Vietnamese vermicelli noodles, fresh herbs, vegetables and plenty of nuoc cham.