How to Make It
Heat the oil in a medium saucepan. Add the garlic and ginger and cook over moderately high heat until fragrant, about 1 minute. Add the chicken stock, vinegar, ketchup, sugar, soy sauce and chili paste and cook over moderately low heat until reduced to 3/4 cup, about 20 minutes. Stir the cornstarch mixture, add it to the sauce and cook until thickened, about 1 minute. Remove from the heat, cover and keep warm.
Preheat the broiler; set the rack 8 inches from the heat. Arrange the chicken on a broiling pan, season with salt and pepper and broil for about 20 minutes, turning occasionally, until just cooked through. Brush the chicken with sauce and return it to the pan. Broil for about 20 minutes longer, turning once and shifting the pan occasionally, until golden and caramelized. Brush occasionally with additional sauce. Serve hot.