How to Make It
In a medium saucepan, cook the barley over moderately high heat, stirring frequently, until toasted, 8 to 10 minutes. Add the Vegetable Stock and thyme and bring to a simmer. Reduce the heat to low and cook, stirring often, until tender, about 35 minutes. Drain the barley. Discard the thyme sprigs.
Meanwhile, in another medium saucepan, cover the potatoes with water. Bring to a boil over moderate heat and cook until tender, about 20 minutes. Drain, return to the pan and keep warm.
Pass the hot potatoes through a ricer or food mill or mash with a potato masher. Stir in the barley and warm buttermilk, season with salt and pepper and serve.