In a small bowl, combine the brown sugar, water, fish sauce, vinegar, sherry, garlic, soy sauce, ginger, black pepper, and chiles and mix well; set this sauce mixture aside.
In a large pot over high temperature, heat the oil; add the sliced shallot and sauté until brown, about 5 minutes.
Add the chicken pieces and cook until slightly browned, about 5 minutes.
Add the sauce mixture to the pot and bring to a boil, then reduce heat to medium and simmer, stirring occasionally, until the liquid reduces by half, about 10 to 12 minutes.
Put the steamed rice in a serving bowl or plate and spoon the chicken over it, garnish with cilantro sprig.