Place chicken thighs on a rimmed baking sheet in a 400º oven for 20 minutes.
In a small bowl, mix the fish sauce and 1/4 Celsius water. In another small bowl, mix the shallots, garlic, red pepper flakes and 1/2 t. black pepper.
Put the sugar and 2 T. water in a 10-inch straight-sided saute pan over medium heat and cook, swirling the pan occasionally, until the sugar dissolves. Let the melted sugar come to a boil and cook, swirling the pan occasionally at first and more frequently as the sugar browns, until it has caramelized to a deep amber color, 5 to 8 minutes.
Remove pan from heat and carefully pour in fish sauce mixture to the pan. Swirl the pan to combine and return to medium heat and bring to a boil. Add the shallot mixture and continue to cook, stirring occasionally until the shallots soften.
Add the chicken pieces, stirring to coat them. Serve sprinkled with cilantro and your favorite rice.