Place the pepper-coriander root paste in a large bowl and stir in the fish sauce. Place the chicken pieces in the marinade and turn them to coat well. Allow them to stand, covered, at room temperature for about one hour.
Preheat the grill.
The chicken pieces should be about four to five inches from the coals, bone sides down.
Grill the chicken pieces until the bottom side is starting to brown. This should take from five to ten minutes, depending on the heat of the coals. Turn the chicken over and cook on the other side until golden brown.
When fully cooked, the chicken juices should run clear. Transfer the chicken to a platter.
Serve with the dipping sauce and lots of sticky rice.
Pepper-Coriander Root Flavor Paste
2 teaspoons fresh peppercorns
5 or 6 large cloves of garlic, chopped coarsely
3 tablespoons of coarsely chopped coriander roots
Pinch of sea salt
1 teaspoon Thai fish sauce
Place the peppercorns in a food processor with the garlic and process to a paste. Add the coriander roots and salt and continue processing to a paste. Stir in the fish sauce. This mixture will keep in a well-sealed glass jar for up to 4 days.
Hot and Sweet Dipping Sauce
1/2 cup rice vinegar
1/2 cup sugar
1 or 2 cloves garlic, minced fine
1/4 teaspoon sea salt
1 1/2 teaspoons crushed red chile peppers
Place the vinegar in a small saucepan and heat to a boil. Add the sugar, stirring, until it's completely dissolved. Lower the heat to medium-low and simmer for about 6 minutes.
Use a garlic press to crush the garlic and mix it with the salt to a smooth paste. Stir in the pepper flakes and blend well.
Remove the vinegar mixture from the heat and stir the garlic paste into the mixture. Cool to room temperature.