Grind the coriander root, garlic, and white and black peppercorns with a mortar and pestle until a rough paste is made. Stir in the sugar, salt, light and dark soy sauces, and 1/4 cup of water. Stir until the sugar dissolves.
Put the marinade in a large zip lock bag with the chicken and marinate for 2 - 3 hours at room temperature.
After marinating, mix rice flour into the chicken and marinade until you have a thick batter.
Heat the oil in a deep pot and fry the chicken for about 7 minutes, a few pieces at a time. Serve with sticky rice and crispy fried shallots.