Place chicken in a large bowl with soy sauce and half of the garlic, ginger and chile flakes. Toss well to coat; if desired, cover and refrigerate for several hours or overnight.Advertisement
Heat oil in a large, deep nonstick skillet over medium-high for a minute or so. Remove chicken from marinade (discard marinade) and add chicken to skillet; brown on both sides, turning occasionally for about 10 minutes. Lower heat and cook another 15 minutes or until chicken is cooked through. Remove chicken to a plate.
Over low heat, add sugar, remaining garlic, ginger and chile flakes along with 2 tablespoons of water to the skillet. Raise the heat to high and cook, stirring occasionally, until sugar melts and the sauce thickens, about 2 minutes. Add fish sauce and any juices from chicken plate; cook another minute. Return chicken to skillet, turning several times. Garnish with cilantro, if desired.
Thai fish sauce is available in the international aisle of the supermarket.