How to Make It
In a small nonreactive saucepan, bring the carrot juice and lemon juice to a boil over moderately high heat. Cook until the solids separate from the liquid, about 5 minutes, then strain into a bowl. Return the juice to the pan. Boil over moderately high heat until the juice is reduced to 2/3 cup, about 20 minutes. Transfer the mixture to a bowl and let cool slightly. Whisk in the rice wine vinegar, soy sauce, vegetable oil and chili oil and season with salt. Whisk in the scallion just before serving.