Heat a grill to medium.
Using a mortar and pestle, crush garlic cloves, peppercorns, coriander, lemongrass, and Thai chiles into a chuncky paste. Using a large spoon, transfer the paste to a large mixing bowl. Add the chicken and the remaining ingredients and mix well. Cover and refrigerate for at least 2 hours or up to overnight.
Put the chicken on the grill, skin side down, and brush with the marinade. Grill for about 15 minutes then flip the chicken over and brush with the marinade. Grill the second side for about 15 minutes. Discard the marinade. When the chicken is cooked and tender transfer it to a serving platter and serve with warm Dipping Sauce.
Put all ingredients in a saucepan and put on the grill. Stir and bring to a boil. Move the pan to a cooler part of the grill and let the sauce simmer for 10 to 15 minutes, stirring occasionally. The sauce will reduce and become thick. Serve warm with chicken.
A viewer or guest of the show, who may not be a professional cook, provided this recipe. It has not been tested for home use.