How to Make It
In a medium saucepan, heat the olive oil. Add the bacon and cook over moderate heat, stirring occasionally, until the fat has rendered, about 5 minutes. Add the onion, carrot, celery and garlic and cook, stirring occasionally, until softened, 3 minutes. Stir in the barley and stock and bring to a boil. Cover and cook over moderately low heat until all of the stock has been absorbed and the barley is tender, about 1 hour. Transfer to a bowl and garnish with the toasted walnuts.