Add the remaining 1 tablespoon of grapeseed oil to the skillet. Add the lemongrass and cook over moderately high heat for 1 minute. Add the kale and cook, stirring, until wilted, about 2 minutes. Add the barley and cook for 1 minute. Add the horseradish, tamari and vinegar and cook, stirring, until the pan is nearly dry, about 2 minutes.